Refactor report handling and improve async operations

Refactored the `Report` property to `_report` with nullable support
and updated `EnvelopeKey` to use `init` for immutability.
Made `CreateReport` asynchronous, returning `Task<XtraReport>`,
and removed redundant `BasePdfBytes` property. Simplified predefined
report fetching by removing `ReportStorage.TryGetReport`. Improved
error handling for missing or invalid `pdfBytes` in `CreateReport`.
Made minor formatting and structural improvements for clarity.

COPILOT_CONTEXT.md

@@ -0,0 +1,424 @@
+# EnvelopeGenerator — AI Context Reference
+
+## Purpose
+Digital document signing system with **unified Blazor WASM frontend** for both Senders and Receivers. Senders create envelopes and place signature fields. Receivers view PDFs, sign documents, export stamped PDFs.
+
+**Primary Libraries:** DevExpress + PDF.js (PSPDFKit removed)
+
+---
+
+## Deployment Architecture
+
+**Two Presentation Projects (Both Required):**
+
+1. **EnvelopeGenerator.API** (ASP.NET Core Web API)
+   - Runs independently (development & production)
+   - **YARP Reverse Proxy** configured via `yarp.json`
+   - Proxies requests to:
+     - `EnvelopeGenerator.ReceiverUI` (Blazor WASM)
+     - External Auth.API service
+   - Serves as single entry point for all requests
+
+2. **EnvelopeGenerator.ReceiverUI** (Blazor WebAssembly)
+   - Runs on separate host/port
+   - Accessed **only through API proxy** (not directly)
+   - Serves static files (HTML, JS, CSS, WASM)
+
+**Request Flow:**
+```
+Client ? API:8088 (YARP Proxy) ? ReceiverUI:52936 (Blazor WASM)
+                                ? Auth.API:9090 (External Auth Service)
+```
+
+**Configuration:** `EnvelopeGenerator.API/yarp.json`
+
+---
+
+## ReceiverUI Route Structure
+
+### Root Route
+| Route | File | Purpose |
+|---|---|---|
+| `/` | `Index.razor` | Application entry point (landing page). |
+
+### Sender Routes
+| Route | File | Purpose |
+|---|---|---|
+| `/sender/login` | `LoginSenderPage.razor` | Username/password authentication |
+| `/sender` | `EnvelopeSenderPage.razor` | Sender dashboard (envelope list) |
+
+### Receiver Routes
+| Route | File | Purpose |
+|---|---|---|
+| `/envelope/login/{EnvelopeKey}` | `LoginReceiverPage.razor` | Access code authentication for specific envelope |
+| `/envelope/{EnvelopeKey}` | `EnvelopeReceiverPage.razor` | View & sign envelope (PDF.js viewer) |
+
+**Multi-Envelope Support:** Receivers can login to multiple envelopes simultaneously (per-envelope cookie authentication).
+
+---
+
+## Architecture Evolution
+
+### Old Architecture (Deprecated)
+- **Sender UI:** `EnvelopeGenerator.Web` (Razor Pages + PSPDFKit)
+- **Receiver UI:** `EnvelopeGenerator.ReceiverUI` (Blazor WASM + PDF.js)
+- **Backend:** `EnvelopeGenerator.API`
+
+### Current Architecture
+- **Unified Frontend:** `EnvelopeGenerator.ReceiverUI` (Blazor WASM) — **Both Senders & Receivers**
+- **Backend:** `EnvelopeGenerator.API` — **Both Senders & Receivers**
+- **Libraries:** DevExpress + PDF.js
+- **PSPDFKit:** **REMOVED**
+
+---
+
+## Solution Structure
+
+| Project | Target | Purpose |
+|---|---|---|
+| `EnvelopeGenerator.API` | net8.0 | ASP.NET Core Web API. Backend for **both Senders & Receivers**. Auth, PDF serving, signature endpoints. |
+| `EnvelopeGenerator.ReceiverUI` | net8.0 WASM | **Unified Blazor WebAssembly Frontend**. UI for **both Senders & Receivers**. YARP proxy to API. |
+| `EnvelopeGenerator.Web` | net7/8/9 | **DEPRECATED.** Legacy Razor Pages (Sender UI). No longer used. |
+| `EnvelopeGenerator.Application` | multi | MediatR CQRS handlers. Business logic. |
+| `EnvelopeGenerator.Domain` | multi | Domain models, constants, interfaces. |
+| `EnvelopeGenerator.Infrastructure` | multi | EF Core repos, DB context. |
+| `EnvelopeGenerator.PdfEditor` | multi | iText7 utilities (NOT used in ReceiverUI). |
+| `EnvelopeGenerator.DependencyInjection` | multi | DI registration helpers. |
+| **VB.NET projects** (Service/Form/BBTests) | net462 | **Legacy. Do NOT touch.** |
+
+---
+
+## Key Files & Routes
+
+| File | Route/Purpose |
+|---|---|
+| `ReceiverUI/Pages/Index.razor` | `/` — Application entry point (landing page). |
+| `ReceiverUI/Pages/EnvelopeSenderPage.razor` | `/sender` — Sender dashboard (envelope list). |
+| `ReceiverUI/Pages/EnvelopeReceiverPage.razor` | `/envelope/{key}` — Receiver PDF viewer & signing. |
+| `ReceiverUI/Pages/LoginSenderPage.razor` | `/sender/login` — Sender username/password auth. |
+| `ReceiverUI/Pages/LoginReceiverPage.razor` | `/envelope/login/{EnvelopeKey}` — Receiver access code auth. |
+| `ReceiverUI/wwwroot/js/pdf-viewer.js` | PDF.js wrapper (zoom, pagination, thumbnails). |
+| `ReceiverUI/wwwroot/js/receiver-signature.js` | Signature pad (draw/type/image). |
+| `ReceiverUI/wwwroot/css/envelope-viewer.css` | EnvelopeViewer styles. |
+| `ReceiverUI/Services/AuthService.cs` | Receiver + Sender authentication. |
+| `ReceiverUI/Services/SignatureCacheService.cs` | Signature caching (Redis/SQL). |
+| `API/Controllers/CacheController.cs` | Signature cache endpoints. |
+
+---
+
+## Coordinate System — CRITICAL
+
+**Database Format:** INCHES (GdPicture14 native)  
+**Origin:** Top-left corner  
+**Axes:** X right, Y down
+
+### Conversion Formulas
+
+| From INCHES to | Formula | Example |
+|---|---|---|
+| **DevExpress DX** | `x_DX = x_inches * 100` | 1.5" ? 150 DX |
+| **PDF Points** | `x_pt = x_inches * 72` | 1.5" ? 108 pt |
+| **PDF.js Pixels** | Normalize ? scale | `(x_inches / pageWidth) * canvasWidth * scale` |
+
+**A4 Dimensions:**
+- Width: 8.27" = 595pt = 827 DX
+- Height: 11.69" = 842pt = 1169 DX
+
+### Unit Systems
+
+| System | Unit | Origin | Y-Axis |
+|---|---|---|---|
+| **Database (GdPicture14)** | Inches | Top-left | Down |
+| PDF.js | Pixels | Top-left | Down |
+| iText7 PDF | Points (1/72") | **Bottom-left** | **Up** (flip required) |
+| ~~PSPDFKit~~ | ~~Points~~ | ~~Top-left~~ | **REMOVED** |
+
+---
+
+## EnvelopeReceiver — PDF.js Viewer & Signing
+
+**Route:** `/envelope/{EnvelopeKey}`  
+**Tech:** PDF.js 3.11.174 + Blazor WASM + configurable quality  
+**File:** `ReceiverUI/Pages/EnvelopeReceiverPage.razor`
+
+### Key Features
+1. HiDPI/Retina support (4x quality)
+2. Configurable quality (`appsettings.json`)
+3. Unlimited zoom (50%-300%)
+4. Ctrl+Wheel global zoom
+5. Resizable thumbnail sidebar (150-400px, localStorage)
+6. Responsive (desktop/mobile)
+
+### Configuration
+**File:** `ReceiverUI/wwwroot/appsettings.json`
+
+```json
+{
+  "PdfViewer": {
+    "ThumbnailBaseScale": 0.75,
+    "ThumbnailEnableHiDPI": true,
+    "MainCanvasEnableHiDPI": true,
+    "ZoomStepPercentage": 5
+  }
+}
+```
+
+### JavaScript API
+**File:** `ReceiverUI/wwwroot/js/pdf-viewer.js`
+
+```javascript
+window.pdfViewer = {
+    initialize(canvasId, pdfDataUrl, dotNetRef),
+    renderPage(num),
+    renderSignatureButtons(signatures, pageNum, dotNetRef),
+    applySignature(signatureId, dataUrl, fullName, position, place),
+    zoomIn(), zoomOut(), dispose()
+}
+```
+
+---
+
+## Signature Workflow — EnvelopeReceiver
+
+**IMPORTANT:** iText7 NOT used (GPL license issue). Client-side overlay system only.
+
+### Workflow Steps
+
+1. **Page Load:**
+   - Check `SignatureCacheService` for cached signature
+   - If cached ? skip popup, load signature
+   - If not ? show automatic popup (mandatory)
+
+2. **Signature Popup (DxPopup):**
+   - **Cannot close** (no X, no ESC, no outside-click)
+   - **3 Tabs:** Draw (canvas) / Text (font select) / Image (upload)
+   - **Required:** Full name, Place
+   - **Optional:** Position
+   - **Save ?** Store in `_capturedSignature`, cache via API
+
+3. **Signature Buttons:**
+   - Render purple "Unterschreiben" buttons at signature field positions
+   - Coordinates: INCHES ? POINTS ? Pixels (scaled)
+   - File: `pdf-viewer.js` ? `renderSignatureButtons()`
+
+4. **Apply Signature (Click "Unterschreiben"):**
+   - JS: Remove button, create HTML overlay
+   - Format: Image + separator + text (Name, Position, Place, Date)
+   - **NOT stamped on PDF bytes** (visual overlay only)
+
+5. **Re-rendering:**
+   - Zoom/Page change ? recalculate button positions
+   - Session state: `_capturedSignature` (lost on refresh)
+
+### Data Model
+**File:** `ReceiverUI/Models/SignatureCaptureDto.cs`
+
+```csharp
+public sealed record SignatureCaptureDto {
+    public required string DataUrl { get; init; }    // base64 PNG
+    public required string FullName { get; init; }
+    public string Position { get; init; } = "";      // Optional
+    public required string Place { get; init; }
+}
+```
+
+---
+
+## Signature Caching
+
+**Purpose:** Persist signature across page refreshes (distributed cache: Redis/SQL)
+
+### API Endpoints
+**Controller:** `API/Controllers/CacheController.cs`
+
+- `POST /api/Cache/SignatureCapture/{envelopeKey}` — Save
+- `GET /api/Cache/SignatureCapture/{envelopeKey}` — Load
+- `DELETE /api/Cache/SignatureCapture/{envelopeKey}` — Delete
+
+**Cache Key Format:**
+```
+signature:91751687-8ae6-4777-bf5f-b8846085e62e:{envelopeKey}
+```
+
+**Configuration:** `appsettings.json`
+```json
+{
+  "Cache": {
+    "SignatureCacheExpiration": null  // or "02:00:00" for 2h
+  }
+}
+```
+
+### Service
+**File:** `ReceiverUI/Services/SignatureCacheService.cs`
+
+```csharp
+public class SignatureCacheService {
+    Task SaveSignatureAsync(string envelopeKey, SignatureCaptureDto signature);
+    Task<SignatureCaptureDto?> GetSignatureAsync(string envelopeKey);
+    Task DeleteSignatureAsync(string envelopeKey);
+}
+```
+
+**Error Handling:** Fire-and-forget saves, graceful degradation on load failure.
+
+---
+
+## Sender Login
+
+**Route:** `/sender/login`  
+**File:** `ReceiverUI/Pages/LoginSenderPage.razor`  
+**Tech:** Bootstrap 5 + DevExpress Blazing Berry theme
+
+### AuthService Extension
+**File:** `ReceiverUI/Services/AuthService.cs`
+
+```csharp
+public enum SenderLoginResult { Success, InvalidCredentials, Error }
+
+public async Task<SenderLoginResult> LoginSenderAsync(string username, string password) {
+    var response = await http.PostAsJsonAsync(
+        $"{_api.BaseUrl}/api/auth?cookie=true",
+        new { username, password });
+    
+    return response.StatusCode switch {
+        HttpStatusCode.OK => SenderLoginResult.Success,
+        HttpStatusCode.Unauthorized => SenderLoginResult.InvalidCredentials,
+        _ => SenderLoginResult.Error
+    };
+}
+```
+
+### API Integration
+**Endpoint:** `POST /api/auth?cookie=true`
+
+**Request:**
+```json
+{ "username": "TekH", "password": "***" }
+```
+
+**Response:**
+- `200 OK` ? Cookie set, redirect to `/sender`
+- `401 Unauthorized` ? Show error: "Ungültige Anmeldedaten"
+- Other ? Show error: "Serverfehler"
+
+**Cookie:** HTTP-only, Secure (HTTPS), SameSite=Strict
+
+### UI Flow
+1. User enters username + password
+2. Click "Anmelden" or press Enter
+3. Call `AuthService.LoginSenderAsync()`
+4. Success ? `Navigation.NavigateTo("/sender", forceLoad: true)`
+5. Error ? Display alert
+
+---
+
+## Receiver Login
+
+**Route:** `/envelope/login/{EnvelopeKey}`  
+**File:** `ReceiverUI/Pages/LoginReceiverPage.razor`
+
+**Multi-Envelope Support:** Cookies are stored per-envelope (e.g., `AuthTokenSignFLOWReceiver.{envelopeKey}`), allowing simultaneous authentication for multiple envelopes in the same browser session.
+
+### AuthService Method
+```csharp
+public enum EnvelopeLoginResult { Success, InvalidCode, NotFound, Error }
+
+public async Task<EnvelopeLoginResult> LoginEnvelopeReceiverAsync(string key, string accessCode) {
+    var form = new MultipartFormDataContent();
+    form.Add(new StringContent(accessCode), "AccessCode");
+    
+    var response = await http.PostAsync(
+        $"{_api.BaseUrl}/api/Auth/envelope-receiver/{Uri.EscapeDataString(key)}", form);
+    
+    return response.StatusCode switch {
+        HttpStatusCode.OK => EnvelopeLoginResult.Success,
+        HttpStatusCode.Unauthorized => EnvelopeLoginResult.InvalidCode,
+        HttpStatusCode.NotFound => EnvelopeLoginResult.NotFound,
+        _ => EnvelopeLoginResult.Error
+    };
+}
+```
+
+**Success:** Redirect to `/envelope/{key}`
+
+---
+
+## NuGet Packages (ReceiverUI)
+
+| Package | Version | Purpose |
+|---|---|---|
+| `DevExpress.Blazor.*` | 25.2.3 | UI components (grids, popups, etc.) |
+| `SkiaSharp.*` | 3.119.1 | WASM rendering |
+| ~~`itext`~~ | ~~8.0.5~~ | **NOT USED** (GPL license) |
+
+**External CDN:**
+- PDF.js 3.11.174: `https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js`
+
+---
+
+## Mistakes History — Do NOT Repeat
+
+| Mistake | Why Wrong |
+|---|---|
+| Using iText7 in EnvelopeReceiver | GPL license issue. Use overlay system instead. |
+| Using PSPDFKit | Removed from architecture. Use PDF.js + DevExpress. |
+| Hardcoded quality values in PDF.js | Use `appsettings.json` for configurability. |
+| Complex toolbar layouts | User wants simplicity. Keep horizontal layout. |
+| Over-designed UI (gradients/badges) | User prefers simple text labels. |
+| Ignoring "revert" instructions | Revert HTML structure, not just CSS. |
+| `BottomMarginBand` for signatures | Repeats on every page. Use DetailBand. |
+| `imageY = (page-1) * 1169 + ann.Y` | Inflates DetailBand. Calculate per-page. |
+
+---
+
+## Development Notes
+
+### Deprecated Projects
+**DO NOT USE:**
+- `EnvelopeGenerator.Web` (Razor Pages) — Replaced by unified ReceiverUI
+- PSPDFKit — Removed, use PDF.js + DevExpress instead
+
+### Legacy Projects (VB.NET)
+**DO NOT TOUCH:** `EnvelopeGenerator.Service`, `EnvelopeGenerator.Form`, `EnvelopeGenerator.BBTests`
+
+### Signature Coordinate Evidence
+**File:** `EnvelopeGenerator.Form/frmFieldEditor.vb` (VB.NET)
+
+```vb
+Private Const SIGNATURE_WIDTH As Single = 1.77   ' inches
+Private Const SIGNATURE_HEIGHT As Single = 1.96  ' inches
+
+Sub LoadAnnotation(pElement As Signature, ...)
+    oAnnotation.Left = CSng(pElement.X)    ' Direct INCHES assignment
+    oAnnotation.Top = CSng(pElement.Y)
+End Sub
+```
+
+Proves database uses INCHES natively.
+
+---
+
+## Quick Reference
+
+### When working with coordinates:
+1. **Database ? UI:** INCHES × 72 = PDF Points
+2. **UI ? Display:** Points × scale = Pixels
+3. **iText7 stamping:** Flip Y-axis (top-down ? bottom-up)
+
+### When adding features:
+1. Check `Mistakes History` first
+2. Prefer simplicity over complexity
+3. Use `appsettings.json` for configuration
+4. Keep consistent with existing design (Bootstrap 5 + Blazing Berry)
+5. **Unified frontend:** ReceiverUI serves both Senders and Receivers
+
+### When debugging:
+1. **Coordinates:** Always check unit system (inches/points/pixels)
+2. **Authentication:** Check cookie name/domain/SameSite
+3. **Cache:** Check Redis/SQL connection + key format
+4. **Frontend confusion:** Only use ReceiverUI (Web is deprecated)
+
+---
+
+**Last Updated:** Session 19 (Razor file naming convention + Index route proxy)

EnvelopeGenerator.API/AuthScheme.cs

@@ -0,0 +1,17 @@
+namespace EnvelopeGenerator.API;
+
+/// <summary>
+/// 
+/// </summary>
+public static class AuthScheme
+{
+    /// <summary>
+    /// Scheme name used for per-envelope receiver JWT authentication.
+    /// </summary>
+    public const string Receiver = "EnvelopeGenerator.API.ReceiverJWT";
+
+    /// <summary>
+    /// Scheme name used for per-envelope sender JWT authentication.
+    /// </summary>
+    public const string Sender = "EnvelopeGenerator.API.SenderJWT";
+}

EnvelopeGenerator.API/Program.cs

@@ -21,6 +21,7 @@ using EnvelopeGenerator.API.Options;
 using NLog.Web;
 using NLog;
 using DigitalData.Auth.Claims;
+using EnvelopeGenerator.API;
 
 var logger = LogManager.Setup().LoadConfigurationFromAppSettings().GetCurrentClassLogger();
 logger.Info("Logging initialized!");
@@ -130,15 +131,12 @@ try
 
     var authTokenKeys = config.GetOrDefault<AuthTokenKeys>();
 
-    // Scheme name used for per-envelope receiver JWT authentication.
-    const string EnvelopeReceiverScheme = "EnvelopeReceiverJwt";
-
     builder.Services.AddAuthentication(options =>
     {
         options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
         options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
     })
-        .AddJwtBearer(opt =>
+        .AddJwtBearer(AuthScheme.Sender, opt =>
         {
             opt.TokenValidationParameters = new TokenValidationParameters
             {
@@ -176,7 +174,7 @@ try
         // last path segment of the request URL.
         // This enables simultaneous authentication for multiple envelopes
         // within the same browser session.
-        .AddJwtBearer(EnvelopeReceiverScheme, opt =>
+        .AddJwtBearer(AuthScheme.Receiver, opt =>
         {
             opt.TokenValidationParameters = new TokenValidationParameters
             {
@@ -240,19 +238,16 @@ try
     });
 
     builder.Services.AddAuthorizationBuilder()
-        .AddPolicy(AuthPolicy.SenderOrReceiver, policy =>
-            policy.RequireRole(Role.Sender, Role.Receiver.Full))
-        .AddPolicy(AuthPolicy.Sender, policy =>
-            policy.RequireRole(Role.Sender))
-        // Per-envelope policy: uses the dedicated EnvelopeReceiverJwt scheme so it
-        // never conflicts with the default JwtBearer scheme.
-        .AddPolicy(AuthPolicy.Receiver, policy =>
-            policy
-                .AddAuthenticationSchemes(EnvelopeReceiverScheme)
-                .RequireAuthenticatedUser()
+        .AddPolicy(AuthPolicy.SenderOrReceiver, policy => policy.RequireRole(Role.Sender, Role.Receiver.Full))
+
+        .AddPolicy(AuthPolicy.Sender, policy => policy
+            .RequireRole(Role.Sender)
+            .AddAuthenticationSchemes(AuthScheme.Sender))
+        .AddPolicy(AuthPolicy.Receiver, policy => policy
+            .AddAuthenticationSchemes(AuthScheme.Receiver)
+            .RequireAuthenticatedUser()
             .RequireRole(Role.Receiver.Full, "receiver"))
-        .AddPolicy(AuthPolicy.ReceiverTFA, policy =>
-            policy.RequireRole(Role.Receiver.TFA));
+        .AddPolicy(AuthPolicy.ReceiverTFA, policy => policy.RequireRole(Role.Receiver.TFA));
 
     // User manager
 #pragma warning disable CS0618 // Type or member is obsolete

EnvelopeGenerator.API/yarp.json

@@ -1,21 +1,16 @@
 {
 "ReverseProxy": {
   "Routes": {
-    "receiver-ui-receiver": {
+    "receiver-ui-root": {
       "ClusterId": "receiver-ui",
-      "Order": 100,
+      "Order": 300,
       "Match": {
-        "Path": "/receiver/{**catch-all}",
+        "Path": "/",
         "Methods": [ "GET", "HEAD" ]
-      }
-    },
-    "receiver-ui-login": {
-      "ClusterId": "receiver-ui",
-      "Order": 100,
-      "Match": {
-        "Path": "/login/{**catch-all}",
-        "Methods": [ "GET", "HEAD" ]
-      }
+      },
+      "Transforms": [
+        { "PathSet": "/index.html" }
+      ]
     },
     "receiver-ui-sender": {
       "ClusterId": "receiver-ui",
@@ -23,7 +18,10 @@
       "Match": {
         "Path": "/sender/{**catch-all}",
         "Methods": [ "GET", "HEAD" ]
-      }
+      },
+      "Transforms": [
+        { "PathSet": "/index.html" }
+      ]
     },
     "receiver-ui-envelope": {
       "ClusterId": "receiver-ui",
@@ -36,6 +34,17 @@
         { "PathSet": "/index.html" }
       ]
     },
+    "receiver-ui-envelope-dxreportviewer": {
+      "ClusterId": "receiver-ui",
+      "Order": 90,
+      "Match": {
+        "Path": "/envelope/{EnvelopeKey}/DxReportViewer",
+        "Methods": [ "GET", "HEAD" ]
+      },
+      "Transforms": [
+        { "PathSet": "/index.html" }
+      ]
+    },
     "receiver-ui-blazor-framework": {
       "ClusterId": "receiver-ui",
       "Order": 50,

EnvelopeGenerator.Application/Common/Dto/MappingProfile.cs

@@ -40,7 +40,9 @@ public class MappingProfile : Profile
         // DTO to Entity mappings
         CreateMap<ConfigDto, Config>();
         CreateMap<DocReceiverElementDto, DocReceiverElement>();
-        CreateMap<Signature, DocReceiverElement>().MapChangedWhen();
+        CreateMap<Signature, DocReceiverElement>()
+            .ForMember(dest => dest.Ink, opt => opt.MapFrom(src => src.DataUrl.MapDataUrlToRequiredBytes()))
+            .MapChangedWhen();
         CreateMap<DocumentStatusDto, DocumentStatus>();
         CreateMap<EmailTemplateDto, EmailTemplate>();
         CreateMap<EnvelopeDto, Envelope>();

EnvelopeGenerator.Application/Common/Dto/Signature.cs

@@ -15,7 +15,7 @@ public sealed record Signature
     /// <summary>
     /// TBDD_DOCUMENT_RECEIVER_ELEMENT.ID - identifies the specific signature field on the PDF page.
     /// </summary>
-    public required int ElementId { get; init; }
+    public required int Id { get; init; }
 
     /// <summary>
     /// Base64-encoded data URL of the signature image.

EnvelopeGenerator.Application/Common/Extensions/AutoMapperAuditingExtensions.cs

@@ -1,5 +1,6 @@
 using AutoMapper;
 using EnvelopeGenerator.Domain.Interfaces.Auditing;
+using System;
 
 namespace EnvelopeGenerator.Application.Common.Extensions;
 
@@ -21,4 +22,21 @@ public static class AutoMapperAuditingExtensions
     public static IMappingExpression<TSource, TDestination> MapChangedWhen<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
         where TDestination : IHasChangedWhen
         => expression.ForMember(dest => dest.ChangedWhen, opt => opt.MapFrom(_ => DateTime.Now));
+
+    /// <summary>
+    /// Converts a base64 data URL string to a byte array.
+    /// Handles data URLs in the format: "data:image/png;base64,iVBORw0KG..."
+    /// </summary>
+    /// <param name="dataUrl">The base64 data URL string from Canvas.toDataURL()</param>
+    /// <returns>The decoded byte array, or null if the input is null or empty</returns>
+    public static byte[]? MapDataUrlToRequiredBytes(this string dataUrl)
+    {
+        // Remove data URL prefix (e.g., "data:image/png;base64,")
+        var base64Index = dataUrl.IndexOf(',', StringComparison.Ordinal);
+        if (base64Index == -1)
+            throw new ArgumentException("Invalid data URL format. Unable to extract base64 data.", nameof(dataUrl));
+
+        var base64Data = dataUrl[(base64Index + 1)..];
+        return Convert.FromBase64String(base64Data);
+    }
 }

EnvelopeGenerator.Application/DocReceiverElements/Behaviors/AnnotationBehavior.cs

@@ -1,4 +1,5 @@
 using DigitalData.Core.Abstraction.Application.Repository;
+using DigitalData.Core.Exceptions;
 using EnvelopeGenerator.Application.Common.Dto;
 using EnvelopeGenerator.Application.DocReceiverElements.Commands;
 using EnvelopeGenerator.Domain.Entities;
@@ -10,13 +11,13 @@ namespace EnvelopeGenerator.Application.DocReceiverElements.Behaviors;
 /// Pipeline behavior that saves annotations.
 /// Executes first in the signing process.
 /// </summary>
-[Obsolete("This notification is deprecated. Use Signature.Commands.SignCommand instead.")]
+[Obsolete("The PSPDFKit library is deprecated.")]
 public class AnnotationBehavior : IPipelineBehavior<SigningCommand, Unit>
 {
     private readonly IRepository<ElementAnnotation> _repo;
 
     /// <summary>
-    /// 
+    /// Initializes a new instance of the <see cref="AnnotationBehavior"/> class.
     /// </summary>
     /// <param name="repository"></param>
     public AnnotationBehavior(IRepository<ElementAnnotation> repository)
@@ -29,13 +30,21 @@ public class AnnotationBehavior : IPipelineBehavior<SigningCommand, Unit>
     /// </summary>
     /// <param name="request"></param>
     /// <param name="next"></param>
-    /// <param name="cancellationToken"></param>
+    /// <param name="cancel"></param>
     /// <returns></returns>
-    public async Task<Unit> Handle(SigningCommand request, RequestHandlerDelegate<Unit> next, CancellationToken cancellationToken)
+    public async Task<Unit> Handle(SigningCommand request, RequestHandlerDelegate<Unit> next, CancellationToken cancel)
     {
-        if (request.PsPdfKitAnnotation is PsPdfKitAnnotation annot)
-            await _repo.CreateAsync(annot.Structured, cancellationToken);
+        if(request.ReceiverAppType != ReceiverAppType.LegacyWeb)
+            if(request.PsPdfKitAnnotation is null)
+                return await next(cancel);
+            else
+                throw new BadRequestException("PsPdfKit Annotation are only supported for the legacy web receiver type.");
 
-        return await next(cancellationToken);
+        if (request.PsPdfKitAnnotation is PsPdfKitAnnotation annot)
+                await _repo.CreateAsync(annot.Structured, cancel);
+            else
+                throw new BadRequestException("Annotation data is missing or invalid.");
+
+            return await next(cancel);
     }
 }

EnvelopeGenerator.Application/DocReceiverElements/Behaviors/SaveSignatureBehavior.cs

@@ -1,22 +1,11 @@
+using AutoMapper;
+using DigitalData.Core.Abstraction.Application.Repository;
+using DigitalData.Core.Exceptions;
 using EnvelopeGenerator.Application.Common.Dto;
-using EnvelopeGenerator.Application.DocStatus.Commands;
-using EnvelopeGenerator.Domain.Constants;
+using EnvelopeGenerator.Application.DocReceiverElements.Commands;
+using EnvelopeGenerator.Domain.Entities;
 using MediatR;
-using System.Text.Json;
-
-<<<<<<< TODO: Unmerged change from project 'EnvelopeGenerator.Application (net8.0)', Before:
-=======
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand.SigningCommand;
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand;
->>>>>>> After
-
-<<<<<<< TODO: Unmerged change from project 'EnvelopeGenerator.Application (net9.0)', Before:
-=======
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand;
->>>>>>> After
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand.SigningCommand.SigningCommand;
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand.SigningCommand;
-using EnvelopeGenerator.Application.DocReceiverElements.Commands.SigningCommand;
+using Microsoft.EntityFrameworkCore;
 
 namespace EnvelopeGenerator.Application.DocReceiverElements.Behaviors;
 
@@ -28,13 +17,22 @@ public class SaveSignatureBehavior : IPipelineBehavior<SigningCommand, Unit>
 {
     private readonly ISender _sender;
 
+    private readonly IRepository<DocReceiverElement> _elementRepo;
+
+    private readonly IMapper _mapper;
+
     /// <summary>
     /// 
     /// </summary>
     /// <param name="sender"></param>
-    public SaveSignatureBehavior(ISender sender)
+    /// <param name="elementRepo"></param>
+    /// <param name="mapper"></param>
+    public SaveSignatureBehavior(ISender sender, IRepository<DocReceiverElement> elementRepo, IMapper mapper)
     {
         _sender = sender;
+        _elementRepo = elementRepo;
+        _elementRepo = elementRepo;
+        _mapper = mapper;
     }
 
     /// <summary>
@@ -42,10 +40,31 @@ public class SaveSignatureBehavior : IPipelineBehavior<SigningCommand, Unit>
     /// </summary>
     /// <param name="request"></param>
     /// <param name="next"></param>
-    /// <param name="cancellationToken"></param>
+    /// <param name="cancel"></param>
     /// <returns></returns>
-    public async Task<Unit> Handle(SigningCommand request, RequestHandlerDelegate<Unit> next, CancellationToken cancellationToken)
+    public async Task<Unit> Handle(SigningCommand request, RequestHandlerDelegate<Unit> next, CancellationToken cancel)
     {
-        return await next(cancellationToken);
+        if (request.ReceiverAppType == ReceiverAppType.LegacyWeb)
+            return await next(cancel);
+        else if(request.Signatures is not IEnumerable<Signature> signatures)
+            throw new BadRequestException($"Signatures are required for saving signature behavior.");
+
+        var elements = await _elementRepo
+            .Where(e => e.Document.EnvelopeId == request.Envelope.Id)
+            .Where(e => e.ReceiverId == request.Receiver.Id)
+            .ToListAsync(cancel);
+
+        foreach (var element in elements)
+        {
+            var signatures = request.Signatures.Where(s => s.Id == element.Id).ToList();
+            if(signatures.Count == 0)
+                throw new BadRequestException("No signature found for element with id {element.Id}.");
+            else if(signatures.Count > 1)
+                throw new BadRequestException("Multiple signatures found for element with id {element.Id}.");
+            
+            await _elementRepo.UpdateAsync(signatures.First(), e => e.Id == element.Id, cancel);
+        }
+
+        return await next(cancel);
     }
 }

EnvelopeGenerator.Application/DocReceiverElements/Commands/SigningCommand.cs

@@ -36,6 +36,11 @@ public record SigningCommand : EnvelopeReceiverQueryBase, IRequest
     /// 
     /// </summary>
     public IEnumerable<Signature>? Signatures { get; init; }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public ReceiverAppType ReceiverAppType { get; init; } = ReceiverAppType.ReceiverUI;
 }
 
 /// <summary>
@@ -55,3 +60,19 @@ public class SignCommandHandler : IRequestHandler<SigningCommand>
         return Task.CompletedTask;
     }
 }
+
+/// <summary>
+/// 
+/// </summary>
+public enum ReceiverAppType
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    ReceiverUI = 0,
+
+    /// <summary>
+    /// 
+    /// </summary>
+    LegacyWeb = 1,
+}

EnvelopeGenerator.ReceiverUI/Options/ApiOptions.cs

@@ -6,5 +6,5 @@ public class ApiOptions
 
     public string BaseUrl { get; set; } = string.Empty;
 
-    public bool ForceToUseFakeDocument { get; set; } = false;
+    public bool UsePredefinedReports { get; set; } = false;
 }

EnvelopeGenerator.ReceiverUI/Pages/EnvelopeReceiverPage.razor

@@ -16,7 +16,7 @@
 @inject EnvelopeGenerator.ReceiverUI.Services.AuthService AuthService
 @inject EnvelopeGenerator.ReceiverUI.Services.EnvelopeReceiverService EnvelopeReceiverService
 @inject AppVersionService AppVersion
-@inject ILogger<EnvelopeViewer> logger
+@inject ILogger<EnvelopeReceiverPage> logger
 @implements IAsyncDisposable
 
 <link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
@@ -511,7 +511,7 @@ int _totalPages = 0;
 int _currentZoom = 150;
 bool _showThumbnails = true;
 bool _isLoggingOut = false;
-DotNetObjectReference<EnvelopeViewer>? _dotNetRef;
+DotNetObjectReference<EnvelopeReceiverPage>? _dotNetRef;
 IReadOnlyList<SignatureDto> _signatures = [];
 EnvelopeReceiverDto? _envelopeReceiver;
 
@@ -545,7 +545,7 @@ const int MaxThumbnailWidth = 400;
         _isLoggingOut = true;
         await InvokeAsync(StateHasChanged);
         await AuthService.LogoutEnvelopeReceiverAsync(EnvelopeKey);
-        Navigation.NavigateTo($"/login/{Uri.EscapeDataString(EnvelopeKey)}", forceLoad: true);
+        Navigation.NavigateTo($"/envelope/login/{Uri.EscapeDataString(EnvelopeKey)}", forceLoad: true);
     }
 
     protected override async Task OnInitializedAsync() {
@@ -558,24 +558,28 @@ const int MaxThumbnailWidth = 400;
         // Check authentication
         var hasAccess = await AuthService.CheckEnvelopeAccessAsync(EnvelopeKey);
         if (!hasAccess) {
-            Navigation.NavigateTo($"/login/{Uri.EscapeDataString(EnvelopeKey)}");
+            Navigation.NavigateTo($"/envelope/login/{Uri.EscapeDataString(EnvelopeKey)}");
             return;
         }
 
         try {
-            var (pdfBytes, statusCode) = await DocumentService.GetDocumentAsync(EnvelopeKey);
+            var pdfBytes = await DocumentService.GetDocumentAsync(EnvelopeKey);
 
             if (pdfBytes is { Length: > 0 }) {
                 var base64 = Convert.ToBase64String(pdfBytes);
                 _pdfDataUrl = $"data:application/pdf;base64,{base64}";
             } else {
-                _errorMessage = $"Dokument konnte nicht geladen werden. HTTP Status: {statusCode}";
+                _errorMessage = "Dokument konnte nicht geladen werden: Keine Daten empfangen.";
             }
 
             var signatures = await SignatureService.GetAsync(EnvelopeKey);
             _signatures = signatures.Convert(UnitOfLength.Point);
 
             _envelopeReceiver = await EnvelopeReceiverService.GetAsync(EnvelopeKey);
+            if (_envelopeReceiver is null)
+            {
+                logger.LogWarning("Envelope receiver data is null for envelope {EnvelopeKey}", EnvelopeKey);
+            }
 
             await JSRuntime.InvokeVoidAsync("console.log", "Loaded signatures:", _signatures);
 
@@ -608,8 +612,12 @@ const int MaxThumbnailWidth = 400;
                 _popupValidationMessage = null;
             }
 
+        } catch (HttpRequestException ex) {
+            _errorMessage = $"Dokument konnte nicht geladen werden: {ex.Message}";
+            logger.LogError(ex, "Failed to load document for envelope {EnvelopeKey}", EnvelopeKey);
         } catch (Exception ex) {
             _errorMessage = $"Fehler: {ex.Message}";
+            logger.LogError(ex, "Unexpected error during initialization for envelope {EnvelopeKey}", EnvelopeKey);
         }
 
         _isLoading = false;

EnvelopeGenerator.ReceiverUI/Pages/EnvelopeReceiverPage_DxReportViewer.razor

@@ -0,0 +1,49 @@
+@page "/envelope/{EnvelopeKey}/DxReportViewer"
+@using XtraReport = DevExpress.XtraReports.UI.XtraReport
+@using DevExpress.Blazor.Reporting
+@using Microsoft.Extensions.Options
+@using EnvelopeGenerator.ReceiverUI.Options
+@using EnvelopeGenerator.ReceiverUI.Services
+@inject InMemoryReportStorageWebExtension ReportStorage
+@inject DocumentService DocumentService
+@inject IOptions<ApiOptions> AppOptions
+
+<link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
+<link href="_content/DevExpress.Blazor.Reporting.Viewer/css/dx-blazor-reporting-components.bs5.css" rel="stylesheet" />
+
+
+@if (_report is not null) {
+    <DxReportViewer Report="_report" RootCssClasses="w-100 h-100" Zoom="1.3" />
+}
+
+@code {
+    [Parameter] public string EnvelopeKey { get; init; } = null!;
+
+    XtraReport? _report = null;
+
+    protected override async Task OnInitializedAsync() 
+    {
+        _report = await CreateReport();
+    }
+
+    async Task<XtraReport> CreateReport()
+    {
+        if (AppOptions.Value.UsePredefinedReports)
+        {
+            return PredefinedReports.ReportsFactory.GetReport("LargeDatasetReport");
+        }
+        else
+        {
+
+            var pdfBytes = await DocumentService.GetDocumentAsync(EnvelopeKey);
+            if (pdfBytes is null || pdfBytes.Length == 0)
+                throw new InvalidOperationException($"No PDF bytes found for EnvelopeKey: {EnvelopeKey}");
+
+            var report = new XtraReport();
+            var detail = new DevExpress.XtraReports.UI.DetailBand();
+            report.Bands.Add(detail);
+            detail.Controls.Add(new DevExpress.XtraReports.UI.XRPdfContent { Source = pdfBytes, GenerateOwnPages = true });
+            return report;
+        }
+    }
+}

EnvelopeGenerator.ReceiverUI/Pages/EnvelopeSenderPage.razor

@@ -0,0 +1,7 @@
+@page "/sender"
+
+<h3>EnvelopeSender</h3>
+
+@code {
+
+}

EnvelopeGenerator.ReceiverUI/Pages/Example/ReportViewer.razor

@@ -342,13 +342,24 @@ Shown="OnPopupShownAsync">
             }
         }
 
-        _annotations = await AnnotationService.GetAnnotationsAsync(EnvelopeKey ?? "fake");
-        _envelopeReceiver = await EnvelopeReceiverService.GetAsync(EnvelopeKey ?? "fake");
+        _annotations = await AnnotationService.GetAnnotationsAsync(EnvelopeKey);
         
-        if (!AppOptions.Value.ForceToUseFakeDocument && !string.IsNullOrWhiteSpace(EnvelopeKey)) {
-            var (pdfBytes, _) = await DocumentService.GetDocumentAsync(EnvelopeKey);
-            if (pdfBytes is { Length: > 0 })
-                _basePdfBytes = pdfBytes;
+        try {
+            _envelopeReceiver = await EnvelopeReceiverService.GetAsync(EnvelopeKey);
+        } catch (HttpRequestException ex) {
+            // Log error but continue - UI will handle null envelope receiver gracefully
+            Console.WriteLine($"Failed to load envelope receiver: {ex.Message}");
+        }
+
+        if (!AppOptions.Value.UsePredefinedReports && !string.IsNullOrWhiteSpace(EnvelopeKey)) {
+            try {
+                var pdfBytes = await DocumentService.GetDocumentAsync(EnvelopeKey);
+                if (pdfBytes is { Length: > 0 })
+                    _basePdfBytes = pdfBytes;
+            } catch (HttpRequestException ex) {
+                // Log error but continue - will use predefined report instead
+                Console.WriteLine($"Failed to load document: {ex.Message}");
+            }
         }
 
         var initialReport = BuildFreshBaseReport();

EnvelopeGenerator.ReceiverUI/Pages/LoginReceiverPage.razor

@@ -1,4 +1,4 @@
-@page "/login/{EnvelopeKey}"
+@page "/envelope/login/{EnvelopeKey}"
 @using EnvelopeGenerator.ReceiverUI.Services
 @inject AuthService AuthService
 @inject NavigationManager Navigation

EnvelopeGenerator.ReceiverUI/Pages/LoginSenderPage.razor

@@ -0,0 +1,172 @@
+@page "/sender/login"
+@using EnvelopeGenerator.ReceiverUI.Services
+@inject AuthService AuthService
+@inject NavigationManager Navigation
+
+<link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
+
+<div class="login-page-wrapper d-flex align-items-center justify-content-center min-vh-100">
+    <div class="login-card card shadow border-0" style="max-width: 440px; width: 100%;">
+
+        <div class="card-header text-white text-center py-4 border-0" style="background: linear-gradient(135deg, #2c3e50 0%, #3498db 100%); border-radius: calc(0.375rem - 1px) calc(0.375rem - 1px) 0 0;">
+            <div class="mb-2">
+                <svg xmlns="http://www.w3.org/2000/svg" width="40" height="40" fill="currentColor" viewBox="0 0 16 16">
+                    <path d="M11 6a3 3 0 1 1-6 0 3 3 0 0 1 6 0z"/>
+                    <path fill-rule="evenodd" d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8zm8-7a7 7 0 0 0-5.468 11.37C3.242 11.226 4.805 10 8 10s4.757 1.225 5.468 2.37A7 7 0 0 0 8 1z"/>
+                </svg>
+            </div>
+            <h5 class="mb-0 fw-semibold">Sender Anmeldung</h5>
+            <p class="mb-0 mt-1 opacity-75" style="font-size: 0.85rem;">Sicherer Zugang zum Sender-Dashboard</p>
+        </div>
+
+        <div class="card-body p-4">
+
+            <p class="text-muted mb-4" style="font-size: 0.875rem; line-height: 1.5;">
+                Bitte melden Sie sich mit Ihren Zugangsdaten an, um auf das Sender-Dashboard zuzugreifen.
+            </p>
+
+            @if (LoginResult == SenderLoginResult.InvalidCredentials) {
+                <div class="alert alert-danger d-flex align-items-start gap-2 py-2" role="alert">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" fill="currentColor" class="flex-shrink-0 mt-1" viewBox="0 0 16 16">
+                        <path d="M16 8A8 8 0 1 1 0 8a8 8 0 0 1 16 0zM5.354 4.646a.5.5 0 1 0-.708.708L7.293 8l-2.647 2.646a.5.5 0 0 0 .708.708L8 8.707l2.646 2.647a.5.5 0 0 0 .708-.708L8.707 8l2.647-2.646a.5.5 0 0 0-.708-.708L8 7.293 5.354 4.646z"/>
+                    </svg>
+                    <div>
+                        <strong>Ungültige Anmeldedaten.</strong><br />
+                        <span style="font-size:0.85rem;">Benutzername oder Passwort ist falsch. Bitte versuchen Sie es erneut.</span>
+                    </div>
+                </div>
+            } else if (LoginResult == SenderLoginResult.Error) {
+                <div class="alert alert-secondary d-flex align-items-start gap-2 py-2" role="alert">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="18" height="18" fill="currentColor" class="flex-shrink-0 mt-1" viewBox="0 0 16 16">
+                        <path d="M8 15A7 7 0 1 1 8 1a7 7 0 0 1 0 14zm0 1A8 8 0 1 0 8 0a8 8 0 0 0 0 16z"/>
+                        <path d="M7.002 11a1 1 0 1 1 2 0 1 1 0 0 1-2 0zM7.1 4.995a.905.905 0 1 1 1.8 0l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 4.995z"/>
+                    </svg>
+                    <div>
+                        <strong>Serverfehler.</strong><br />
+                        <span style="font-size:0.85rem;">Ein unerwarteter Fehler ist aufgetreten. Bitte versuchen Sie es später erneut.</span>
+                    </div>
+                </div>
+            }
+
+            <div class="mb-3">
+                <label class="form-label fw-medium" for="login-username">
+                    Benutzername
+                    <span class="text-danger ms-1">*</span>
+                </label>
+                <div class="input-group">
+                    <span class="input-group-text bg-light">
+                        <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="#6c757d" viewBox="0 0 16 16">
+                            <path d="M3 14s-1 0-1-1 1-4 6-4 6 3 6 4-1 1-1 1H3Zm5-6a3 3 0 1 0 0-6 3 3 0 0 0 0 6Z"/>
+                        </svg>
+                    </span>
+                    <input id="login-username"
+                           type="text"
+                           class="form-control @(LoginResult == SenderLoginResult.InvalidCredentials ? "is-invalid" : null)"
+                           placeholder="Benutzername eingeben"
+                           @bind="Username"
+                           @bind:event="oninput"
+                           @onkeydown="OnKeyDownAsync"
+                           disabled="@IsLoading"
+                           autocomplete="username" />
+                </div>
+            </div>
+
+            <div class="mb-4">
+                <label class="form-label fw-medium" for="login-password">
+                    Passwort
+                    <span class="text-danger ms-1">*</span>
+                </label>
+                <div class="input-group">
+                    <span class="input-group-text bg-light border-end-0">
+                        <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="#6c757d" viewBox="0 0 16 16">
+                            <path d="M8 1a2 2 0 0 1 2 2v4H6V3a2 2 0 0 1 2-2zm3 6V3a3 3 0 0 0-6 0v4a2 2 0 0 0-2 2v5a2 2 0 0 0 2 2h6a2 2 0 0 0 2-2V9a2 2 0 0 0-2-2z"/>
+                        </svg>
+                    </span>
+                    <input id="login-password"
+                           type="@(ShowPassword ? "text" : "password")"
+                           class="form-control border-start-0 border-end-0 @(LoginResult == SenderLoginResult.InvalidCredentials ? "is-invalid" : null)"
+                           placeholder="Passwort eingeben"
+                           @bind="Password"
+                           @bind:event="oninput"
+                           @onkeydown="OnKeyDownAsync"
+                           disabled="@IsLoading"
+                           autocomplete="current-password" />
+                    <button type="button"
+                            class="btn btn-outline-secondary border-start-0"
+                            style="border-left: none;"
+                            tabindex="-1"
+                            @onclick="() => ShowPassword = !ShowPassword">
+                        @if (ShowPassword) {
+                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
+                                <path d="M13.359 11.238C15.06 9.72 16 8 16 8s-3-5.5-8-5.5a7.028 7.028 0 0 0-2.79.588l.77.771A5.944 5.944 0 0 1 8 3.5c2.12 0 3.879 1.168 5.168 2.457A13.134 13.134 0 0 1 14.828 8c-.058.087-.122.183-.195.288-.335.48-.83 1.12-1.465 1.755-.165.165-.337.328-.517.486l.708.709z"/>
+                                <path d="M11.297 9.176a3.5 3.5 0 0 0-4.474-4.474l.823.823a2.5 2.5 0 0 1 2.829 2.829l.822.822zm-2.943 1.299.822.822a3.5 3.5 0 0 1-4.474-4.474l.823.823a2.5 2.5 0 0 0 2.829 2.829z"/>
+                                <path d="M3.35 5.47c-.18.16-.353.322-.518.487A13.134 13.134 0 0 0 1.172 8l.195.288c.335.48.83 1.12 1.465 1.755C4.121 11.332 5.881 12.5 8 12.5c.716 0 1.39-.133 2.02-.36l.77.772A7.029 7.029 0 0 1 8 13.5C3 13.5 0 8 0 8s.939-1.721 2.641-3.238l.708.709z"/>
+                                <path fill-rule="evenodd" d="M13.646 14.354l-12-12 .708-.708 12 12-.708.708z"/>
+                            </svg>
+                        } else {
+                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
+                                <path d="M16 8s-3-5.5-8-5.5S0 8 0 8s3 5.5 8 5.5S16 8 16 8zM1.173 8a13.133 13.133 0 0 1 1.66-2.043C4.12 4.668 5.88 3.5 8 3.5c2.12 0 3.879 1.168 5.168 2.457A13.133 13.133 0 0 1 14.828 8c-.058.087-.122.183-.195.288-.335.48-.83 1.12-1.465 1.755C11.879 11.332 10.119 12.5 8 12.5c-2.12 0-3.879-1.168-5.168-2.457A13.134 13.134 0 0 1 1.172 8z"/>
+                                <path d="M8 5.5a2.5 2.5 0 1 0 0 5 2.5 2.5 0 0 0 0-5zM4.5 8a3.5 3.5 0 1 1 7 0 3.5 3.5 0 0 1-7 0z"/>
+                            </svg>
+                        }
+                    </button>
+                </div>
+            </div>
+
+            <button class="btn btn-primary w-100 py-2 fw-medium"
+                    style="background: linear-gradient(135deg, #2c3e50 0%, #3498db 100%); border: none;"
+                    @onclick="SubmitAsync"
+                    disabled="@(IsLoading || string.IsNullOrWhiteSpace(Username) || string.IsNullOrWhiteSpace(Password))">
+                @if (IsLoading) {
+                    <span class="spinner-border spinner-border-sm me-2" role="status" aria-hidden="true"></span>
+                    <span>Anmelden …</span>
+                } else {
+                    <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="me-2" viewBox="0 0 16 16">
+                        <path fill-rule="evenodd" d="M10 3.5a.5.5 0 0 0-.5-.5h-8a.5.5 0 0 0-.5.5v9a.5.5 0 0 0 .5.5h8a.5.5 0 0 0 .5-.5v-2a.5.5 0 0 1 1 0v2A1.5 1.5 0 0 1 9.5 14h-8A1.5 1.5 0 0 1 0 12.5v-9A1.5 1.5 0 0 1 1.5 2h8A1.5 1.5 0 0 1 11 3.5v2a.5.5 0 0 1-1 0v-2z"/>
+                        <path fill-rule="evenodd" d="M4.146 8.354a.5.5 0 0 1 0-.708l3-3a.5.5 0 1 1 .708.708L5.707 7.5H14.5a.5.5 0 0 1 0 1H5.707l2.147 2.146a.5.5 0 0 1-.708.708l-3-3z"/>
+                    </svg>
+                    <span>Anmelden</span>
+                }
+            </button>
+
+        </div>
+
+        <div class="card-footer text-center text-muted py-3 border-0 bg-transparent" style="font-size: 0.78rem;">
+            Bei Problemen wenden Sie sich bitte an den Administrator.
+        </div>
+
+    </div>
+</div>
+
+@code {
+    string Username = string.Empty;
+    string Password = string.Empty;
+    bool ShowPassword;
+    bool IsLoading;
+    SenderLoginResult? LoginResult;
+
+    async Task OnKeyDownAsync(Microsoft.AspNetCore.Components.Web.KeyboardEventArgs e) {
+        if (e.Key == "Enter")
+            await SubmitAsync();
+    }
+
+    async Task SubmitAsync() {
+        if (string.IsNullOrWhiteSpace(Username) || string.IsNullOrWhiteSpace(Password) || IsLoading) return;
+
+        IsLoading = true;
+        LoginResult = null;
+        await InvokeAsync(StateHasChanged);
+
+        var result = await AuthService.LoginSenderAsync(Username.Trim(), Password.Trim());
+
+        if (result == SenderLoginResult.Success) {
+            Navigation.NavigateTo("/sender", forceLoad: true);
+            return;
+        }
+
+        LoginResult = result;
+        IsLoading = false;
+        await InvokeAsync(StateHasChanged);
+    }
+}
+

EnvelopeGenerator.ReceiverUI/Services/AuthService.cs

@@ -1,4 +1,5 @@
 using System.Net;
+using System.Net.Http.Json;
 using EnvelopeGenerator.ReceiverUI.Options;
 using Microsoft.Extensions.Options;
 
@@ -6,6 +7,8 @@ namespace EnvelopeGenerator.ReceiverUI.Services;
 
 public enum EnvelopeLoginResult { Success, InvalidCode, NotFound, Error }
 
+public enum SenderLoginResult { Success, InvalidCredentials, Error }
+
 public class AuthService(HttpClient http, IOptions<ApiOptions> apiOptions)
 {
     private readonly ApiOptions _api = apiOptions.Value;
@@ -54,4 +57,25 @@ public class AuthService(HttpClient http, IOptions<ApiOptions> apiOptions)
             null, cancel);
         return response.IsSuccessStatusCode;
     }
+
+    /// <summary>
+    /// Authenticates a sender user with username and password.
+    /// Calls POST /api/auth?cookie=true with JSON body.
+    /// On success the API sets an authentication cookie automatically.
+    /// </summary>
+    public async Task<SenderLoginResult> LoginSenderAsync(string username, string password, CancellationToken cancel = default)
+    {
+        var requestBody = new { username, password };
+
+        var response = await http.PostAsJsonAsync(
+            $"{_api.BaseUrl}/api/auth?cookie=true",
+            requestBody, cancel);
+
+        return response.StatusCode switch
+        {
+            HttpStatusCode.OK => SenderLoginResult.Success,
+            HttpStatusCode.Unauthorized => SenderLoginResult.InvalidCredentials,
+            _ => SenderLoginResult.Error
+        };
+    }
 }

EnvelopeGenerator.ReceiverUI/Services/DocumentService.cs

@@ -11,17 +11,25 @@ public class DocumentService(HttpClient http, IOptions<ApiOptions> apiOptions)
 
     /// <summary>
     /// Fetches the PDF bytes for the given envelope key from the API.
-    /// Returns null bytes with the HTTP status code on failure.
+    /// Throws HttpRequestException on failure with appropriate status code.
     /// </summary>
-    public async Task<(byte[]? Bytes, HttpStatusCode StatusCode)> GetDocumentAsync(string envelopeKey, CancellationToken cancel = default)
+    /// <exception cref="HttpRequestException">Thrown when the API request fails.</exception>
+    public async Task<byte[]?> GetDocumentAsync(string envelopeKey, CancellationToken cancel = default)
     {
         var response = await http.GetAsync($"{_api.BaseUrl}/api/Document/{Uri.EscapeDataString(envelopeKey)}", cancel);
 
         if (!response.IsSuccessStatusCode)
-            return (null, response.StatusCode);
+        {
+            var statusCode = (int)response.StatusCode;
+            var reasonPhrase = response.ReasonPhrase ?? "Unknown error";
+            throw new HttpRequestException(
+                $"Failed to load document. Status: {statusCode} ({reasonPhrase})",
+                null,
+                response.StatusCode);
+        }
 
         var bytes = await response.Content.ReadAsByteArrayAsync(cancel);
-        return (bytes, response.StatusCode);
+        return bytes;
     }
 }
 

EnvelopeGenerator.ReceiverUI/Services/EnvelopeReceiverService.cs

@@ -1,3 +1,4 @@
+using System.Net;
 using System.Net.Http.Json;
 using System.Text.Json;
 using EnvelopeGenerator.ReceiverUI.Models;
@@ -14,13 +15,25 @@ public class EnvelopeReceiverService(HttpClient http, IOptions<ApiOptions> apiOp
 {
     private static readonly JsonSerializerOptions _jsonOptions = new(JsonSerializerDefaults.Web);
 
+    /// <summary>
+    /// Fetches the envelope receiver data for the given envelope key from the API.
+    /// Throws HttpRequestException on failure with appropriate status code.
+    /// </summary>
+    /// <exception cref="HttpRequestException">Thrown when the API request fails.</exception>
     public async Task<EnvelopeReceiverDto?> GetAsync(string envelopeKey, CancellationToken cancel = default)
     {
         var url = $"{apiOptions.Value.BaseUrl}/api/EnvelopeReceiver/{Uri.EscapeDataString(envelopeKey)}";
         var response = await http.GetAsync(url, cancel);
 
         if (!response.IsSuccessStatusCode)
-            return null;
+        {
+            var statusCode = (int)response.StatusCode;
+            var reasonPhrase = response.ReasonPhrase ?? "Unknown error";
+            throw new HttpRequestException(
+                $"Failed to load envelope receiver data. Status: {statusCode} ({reasonPhrase})",
+                null,
+                response.StatusCode);
+        }
 
         return await response.Content.ReadFromJsonAsync<EnvelopeReceiverDto>(_jsonOptions, cancel);
     }

EnvelopeGenerator.ReceiverUI/wwwroot/appsettings.json

@@ -1,7 +1,7 @@
 {
   "Api": {
     "BaseUrl": "",
-    "ForceToUseFakeDocument": false
+    "UsePredefinedReports": false
   },
   "PdfViewer": {
     "ThumbnailBaseScale": 0.75,

EnvelopeGenerator.sln

@@ -21,7 +21,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "core", "core", "{9943209E-1
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{134D4164-B291-4E19-99B9-E4FA3AFAB62C}"
 	ProjectSection(SolutionItems) = preProject
-		COPILOT_CONTEXT_EN.md = COPILOT_CONTEXT_EN.md
+		COPILOT_CONTEXT.md = COPILOT_CONTEXT.md
+		FORM_APPLICATION_CONTEXT.md = FORM_APPLICATION_CONTEXT.md
 	EndProjectSection
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "tests", "tests", "{0CBC2432-A561-4440-89BC-671B66A24146}"

FORM_APPLICATION_CONTEXT.md

@@ -0,0 +1,788 @@
+# EnvelopeGenerator.Form – VB.NET Desktop Application Context
+
+## Purpose
+**Legacy Windows Forms application** for envelope creation, management, and signature field placement. Built with **DevExpress components** and **GdPicture14** for PDF manipulation. This application is being **migrated to ReceiverUI + API** architecture.
+
+**Primary Libraries:** DevExpress XtraGrid/XtraEditors, GdPicture14, VB.NET (.NET Framework 4.6.2)
+
+---
+
+## Application Architecture
+
+### Projects Structure
+| Project | Purpose |
+|---|---|
+| **EnvelopeGenerator.Form** | Main WinForms UI (VB.NET) |
+| **EnvelopeGenerator.CommonServices** | Shared services/helpers |
+| **EnvelopeGenerator.Service** | Windows Service (legacy) |
+| **EnvelopeGenerator.BBTests** | Tests |
+
+### Key Forms (Pages)
+
+#### 1. **frmMain.vb** - Envelope Overview (Dashboard)
+**Route Equivalent:** `/sender` (EnvelopeSenderPage.razor)
+
+**Purpose:** Main dashboard showing all envelopes with status filtering.
+
+**Key Features:**
+- **Tab-based layout** with 2+2 tabs:
+  - **Tab 0:** Active Envelopes (not sent/partially signed)
+  - **Tab 1:** Completed Envelopes (signed/rejected/deleted)
+  - **Tab 2:** Reports (Admin only)
+  - **Tab 3:** Additional Reports (Admin only)
+
+**Envelope Status Colors:**
+| Status | Color | Hex Code | Description |
+|---|---|---|---|
+| `EnvelopePartlySigned` | Green | `#81C784` (GREEN_300) | At least one receiver signed |
+| `EnvelopeQueued` / `EnvelopeSent` | Orange | `#FFB74D` (ORANGE_300) | Sent to receivers, awaiting signatures |
+| `EnvelopeCompletelySigned` | Green | `#81C784` (GREEN_300) | All receivers signed |
+| `EnvelopeDeleted` / `EnvelopeWithdrawn` / `EnvelopeRejected` | Red | `#E57373` (RED_300) | Envelope cancelled/rejected |
+
+**Receiver Status Colors (in detail grids):**
+| Status | Color | Hex Code |
+|---|---|---|
+| `Signed` | Green | `#81C784` (GREEN_300) |
+| `Not Signed` | Red | `#E57373` (RED_300) |
+
+**Grid Layouts:**
+
+1. **GridEnvelopes** (Active):
+   - Columns: ID, Title, Status, Created Date, Creator
+   - **Master-Detail:** Expands to show:
+     - **ViewReceivers:** Receiver list with status colors
+     - **ViewHistory:** Envelope history (status changes, emails sent)
+
+2. **GridCompleted** (Completed):
+   - Same structure as GridEnvelopes
+   - **ViewReceiversCompleted** and **ViewHistoryCompleted** detail grids
+
+**Toolbar Actions:**
+| Button | Action | Enabled When |
+|---|---|---|
+| **Create Envelope** | Opens `frmEnvelopeEditor` | Always |
+| **Edit Envelope** | Opens `frmEnvelopeEditor` with selected envelope | Envelope selected & not sent |
+| **Delete Envelope** | Shows `frmRueckruf` (reason dialog) ? deletes | Envelope selected |
+| **Show Document** | Opens PDF in temp folder | Envelope & document selected |
+| **Contact Receiver** | Opens mailto link | Receiver selected |
+| **Resend Invitation** | Resends email to receiver | Receiver selected |
+| **Send Access Code** | Manually sends access code email | Receiver selected & UseAccessCode=true |
+| **Info Mail** | Opens mailto to support team | Receiver selected (for issues) |
+| **2FA Properties** | Shows `frm2Factor_Properties` dialog | Receiver selected & TFA enabled |
+| **Export Report (EB)** | Exports completed envelope result PDF | Completed envelope selected |
+| **Refresh** | Reloads data | Always |
+| **Export to Excel** | Exports current grid to XLSX | Always |
+
+**Auto-Refresh:** Timer refreshes every N seconds (configurable), but **only when `frmEnvelopeEditor` is not open**.
+
+**Persistence:** Grid layouts saved to `{GridViewName}_UserLayout.xml` in user AppData folder.
+
+---
+
+#### 2. **frmEnvelopeEditor.vb** - Envelope Creation/Edit
+**Route Equivalent:** `/sender/envelope/{id}` (future)
+
+**Purpose:** Create or edit envelope details, add documents, manage receivers.
+
+**Workflow:**
+1. **On New Envelope:** Opens `frmEnvelopeMainData` popup **first** (title, type, settings)
+2. **After popup OK:** Main editor loads
+3. **Add Document:** Single PDF file (via Open Dialog or Drag & Drop)
+4. **Add Receivers:** Grid with auto-complete from previous emails
+5. **Edit Fields:** Opens `frmFieldEditor` for signature field placement
+6. **Send Envelope:** Validates and sends invitations
+
+**UI Layout:**
+- **Top Ribbon:** DevExpress ribbon with actions
+- **Left Panel:** Document list (thumbnail + details)
+- **Right Panel:** Receiver list (name, email, access code, phone)
+- **Bottom Bar:** Envelope ID, Creator Email, Info messages
+
+**Ribbon Actions:**
+| Button | Action | Enabled When |
+|---|---|---|
+| **Add File** | Opens file dialog | No document added |
+| **Merge Files** | Opens `frmOrderFiles` to concatenate PDFs | No document added |
+| **Delete File** | Removes document | Document selected |
+| **Show File** | Opens PDF in default viewer | Document selected |
+| **Edit Fields** | Opens `frmFieldEditor` | Document + receivers exist |
+| **Edit Data** | Opens `frmEnvelopeMainData` | Always |
+| **Save** | Saves envelope without validation | Always |
+| **Send Envelope** | Validates & sends invitations | Document + receivers exist |
+| **Cancel** | Closes with save prompt | Always |
+| **Delete Receiver** | Removes receiver from list | Receiver selected |
+
+**Receiver Grid:**
+- **Columns:** Name, Email, Access Code, Phone (if TFA enabled)
+- **Auto-complete:** Email field suggests previous receivers
+- **Validation:** Email format, Phone format (+49... for TFA)
+- **Access Code:** Auto-generated on email entry (if UseAccessCode=true)
+- **Color Assignment:** Each receiver gets a unique color (for signature fields)
+
+**Document Grid:**
+- **Single file only** (currently limited to 1 PDF)
+- **Thumbnail:** Generated via GdPicture14
+- **Page Count:** Displayed
+
+**Drag & Drop:**
+- Drop PDF files directly onto form
+- Only 1 file allowed
+- Visual feedback (red bar if >1 file)
+
+**Validation:**
+- Title required
+- Message required
+- At least 1 document
+- At least 1 receiver
+- Valid email addresses
+- Valid phone numbers (if TFA enabled)
+- Signature fields exist for each receiver (before sending)
+
+---
+
+#### 3. **frmEnvelopeMainData.vb** - Envelope Settings Popup
+**Route Equivalent:** Part of `/sender/envelope/{id}` (inline in ReceiverUI)
+
+**Purpose:** Configure envelope metadata and behavior. **Shown as modal popup** before main editor.
+
+**Fields:**
+
+| Field | Type | Description |
+|---|---|---|
+| **Title** | Text | Envelope title (required) |
+| **Envelope Type** | Dropdown | Template (ContractType, Language, defaults) |
+| **Language** | Dropdown | de/en |
+| **Use Access Code** | Checkbox | Require 6-digit code for signing |
+| **2FA Enabled** | Checkbox | Require SMS verification (forces Access Code ON) |
+| **Certification Type** | Dropdown | Basic / Advanced / Qualified |
+| **Final Email to Creator** | Dropdown | No / OnComplete / OnCompleteOrReject |
+| **Final Email to Receivers** | Dropdown | No / OnComplete / OnCompleteOrReject |
+| **Send Reminder Emails** | Checkbox | Auto-send reminders |
+| **First Reminder Days** | Number | Days before first reminder |
+| **Reminder Interval Days** | Number | Days between reminders |
+| **Expires When Days** | Number | Days until envelope expires |
+| **Expires Warning Days** | Number | Days before expiry to warn |
+
+**Layout:**
+- **Compact mode:** Only Title, Type, Language visible
+- **Expanded mode:** Click "All Options" to show reminder/expiry settings
+
+**Behavior:**
+- **On Type Selection:** Auto-fills all settings from template
+- **On 2FA Enable:** Forces "Use Access Code" ON and disables checkbox
+- **On New Envelope:** Shows before main editor
+- **On Edit Envelope:** Opens as separate dialog, Type field read-only
+
+**Validation:** Title is required (red border via Adorner).
+
+---
+
+#### 4. **frmFieldEditor.vb** - Signature Field Placement
+**Route Equivalent:** `/sender/envelope/{id}/fields` (future, or inline in editor)
+
+**Purpose:** Place signature fields on PDF pages using **GdPicture14** viewer with annotations.
+
+**UI Layout:**
+- **Left:** PDF Viewer (GdViewer) with annotation tools
+- **Right:** Thumbnail navigator (ThumbnailEx2)
+- **Top:** Toolbar with receiver selector and actions
+
+**Toolbar:**
+| Button | Action |
+|---|---|
+| **Receiver Selector** | Popup menu with receiver names (colored circles) |
+| **Add Signature** | Draws new signature annotation |
+| **Delete** | Removes selected annotation |
+| **Save** | Saves signature fields to database |
+
+**Signature Field Details:**
+- **Size:** 1.77" × 1.96" (4.5cm × 5cm) - **FIXED SIZE**
+- **Color:** Matches receiver color (from grid assignment)
+- **Label:** "SIGNATUR" (or localized "Signature")
+- **Position:** Draggable on PDF canvas
+- **Database Format:** Coordinates stored in **INCHES** (GdPicture native)
+
+**Coordinate System:**
+- **Origin:** Top-left corner
+- **Units:** Inches (not points or pixels)
+- **Axes:** X right, Y down
+- **Storage:** Direct INCHES values (no conversion)
+
+**Evidence from Code:**
+```vb
+Private Const SIGNATURE_WIDTH As Single = 1.77   ' inches
+Private Const SIGNATURE_HEIGHT As Single = 1.96  ' inches
+
+Sub LoadAnnotation(pElement As DocReceiverElement, ...)
+    oAnnotation.Left = CSng(pElement.X)    ' Direct INCHES assignment
+    oAnnotation.Top = CSng(pElement.Y)
+End Sub
+```
+
+**Multi-Receiver Support:**
+- **Receiver switcher:** Click receiver name in popup menu
+- **Current receiver:** Highlighted in toolbar (name + colored circle)
+- **Other receivers' fields:** Shown semi-transparent (30% opacity), not selectable
+- **Save:** Saves current receiver's fields, switches receiver, reloads all annotations
+
+**Annotation Behavior:**
+- **New annotation:** User clicks "Add Signature" ? draws interactive annotation ? auto-sized to 1.77×1.96
+- **Existing annotation:** Loaded from database, locked size (can move but not resize)
+- **Styling:** Filled rectangle with centered text "SIGNATUR"
+- **Validation:** No resize, no text edit, no rotation
+
+**Unsaved Changes Prompt:**
+- On form close: "There are unsaved changes. Save? Yes/No/Cancel"
+- Yes ? Saves ? Closes
+- No ? Discards ? Closes
+- Cancel ? Stays open
+
+---
+
+#### 5. **frmRueckruf.vb** - Delete Reason Dialog
+**Route Equivalent:** Inline confirmation in ReceiverUI
+
+**Purpose:** Capture reason for envelope deletion/withdrawal.
+
+**Fields:**
+- **Envelope ID** (display only)
+- **Envelope Title** (display only)
+- **Reason** (required text box)
+
+**Buttons:**
+- **OK:** Confirms deletion with reason
+- **Cancel:** Cancels operation
+
+**Global Variables:**
+```vb
+Public CurrentEnvelopID As Long
+Public CurrentEnvelopetitle As String
+Public Shared Continue_Reject As Boolean = False
+Public Shared Reject_reason As String = ""
+```
+
+---
+
+#### 6. **frm2Factor_Properties.vb** - 2FA Management
+**Route Equivalent:** `/admin/2fa/{email}` (future admin panel)
+
+**Purpose:** View/manage 2FA settings for a receiver.
+
+**Fields:**
+- **Email Address** (display only)
+- **TOTP Secret Key** (display only)
+- **Registration Deadline** (display only)
+
+**Usage:** Admin tool to debug 2FA issues or reset TOTP secrets.
+
+---
+
+#### 7. **frmOrderFiles.vb** - PDF Merge Tool
+**Route Equivalent:** Inline in ReceiverUI (future)
+
+**Purpose:** Select multiple PDFs and merge them into a single document.
+
+**UI:**
+- **File list:** Selected PDFs
+- **Up/Down buttons:** Reorder files
+- **Add/Remove buttons:** Manage list
+
+**Merge Logic:**
+- Uses GdPicture14 `MergeDocuments()`
+- Output: Single PDF in temp folder
+- Auto-loaded as envelope document
+
+---
+
+## Data Models (Controllers)
+
+### EnvelopeListController
+**Purpose:** Load envelope lists for dashboard grids.
+
+**Methods:**
+- `ListEnvelopes()` ? Active envelopes (not completed)
+- `ListCompleted()` ? Completed envelopes (signed/rejected/deleted)
+- `DeleteEnvelope(envelope, reason)` ? Soft delete with reason
+- `GetPieChart()` ? DevExpress ChartControl (not used)
+- `GetEnvelopeReceiverAddresses(userId)` ? List of previous receiver emails (for auto-complete)
+
+---
+
+### EnvelopeEditorController
+**Purpose:** Manage envelope CRUD and document/receiver operations.
+
+**Key Methods:**
+
+| Method | Purpose |
+|---|---|
+| `CreateDocument(filePath)` | Imports PDF, extracts pages/thumbnail, saves to DB |
+| `DeleteDocument(document)` | Removes document from envelope |
+| `SaveReceivers(envelope, receivers)` | Saves/updates receivers with access codes |
+| `DeleteReceiver(receiver)` | Removes receiver (checks if fields exist) |
+| `ElementsExist(receiverId)` | Checks if signature fields exist for receiver |
+| `SaveEnvelope()` | Persists envelope to database |
+| `SendEnvelope()` | Validates, queues emails, sends invitations |
+| `ValidateEnvelopeForSending(errors)` | Checks all receivers have signature fields |
+| `GetLastNameByEmailAdress(email)` | Returns previous name for email (auto-fill) |
+| `GetLastPhoneByEmailAdress(email)` | Returns previous phone for email (auto-fill) |
+| `DeleteEnvelopeFromDisk(envelope)` | Cleans up temp files |
+
+**ActionService Methods:**
+- `ResendReceiver(envelope, receiver)` ? Resends invitation email
+- `ManuallySendAccessCode(envelope, receiver)` ? Sends access code email
+
+---
+
+### FieldEditorController
+**Purpose:** Manage signature field annotations (DocReceiverElement).
+
+**Key Methods:**
+
+| Method | Purpose |
+|---|---|
+| `LoadElements()` | Loads all signature fields from database |
+| `AddOrUpdateElement(annotation, orientation)` | Converts GdPicture annotation ? DocReceiverElement |
+| `SaveElements(receiverId)` | Persists signature fields for receiver |
+| `DeleteElement(element)` | Removes signature field |
+| `GetElement(annotation)` | Finds element by annotation tag |
+| `GetElementInfo(tag)` | Parses annotation tag (receiverId\|page\|guid) |
+
+**Annotation Tag Format:**
+```
+"{receiverId}|{page}|{elementId}"
+Example: "42|1|-1"  (receiver 42, page 1, unsaved)
+Example: "42|1|137" (receiver 42, page 1, element ID 137)
+```
+
+**Element Coordinate Conversion:**
+```vb
+' Database stores INCHES directly (GdPicture native)
+Sub AddOrUpdateElement(annotation, orientation)
+    element.X = annotation.Left        ' INCHES
+    element.Y = annotation.Top         ' INCHES
+    element.Width = annotation.Width   ' INCHES
+    element.Height = annotation.Height ' INCHES
+    element.Page = currentPage
+End Sub
+```
+
+---
+
+## Migration to ReceiverUI + API
+
+### Mapping Table
+
+| Form Feature | ReceiverUI Equivalent | Status |
+|---|---|---|
+| **frmMain** (Envelope list) | `/sender` (EnvelopeSenderPage.razor) | ? Exists |
+| Tab 0: Active Envelopes | `/sender` default view | ? Grid with filters |
+| Tab 1: Completed Envelopes | `/sender` with status filter | ? Same grid |
+| Status colors (Green/Orange/Red) | CSS classes `.status-signed`, `.status-pending`, etc. | ?? **Needs implementation** |
+| Master-detail grids (Receivers/History) | Expandable rows or modal dialogs | ?? **Needs implementation** |
+| Toolbar: Create Envelope | Button ? `/sender/envelope/new` | ?? **Needs implementation** |
+| Toolbar: Edit Envelope | Button ? `/sender/envelope/{id}` | ?? **Needs implementation** |
+| Toolbar: Delete Envelope | Button ? Shows delete reason modal | ?? **Needs implementation** |
+| Toolbar: Show Document | Downloads PDF | ?? **Needs implementation** |
+| Toolbar: Contact Receiver | `mailto:` link | ?? **Needs implementation** |
+| Toolbar: Resend Invitation | API call ? refresh grid | ?? **Needs implementation** |
+| Toolbar: Export Excel | Download XLSX | ?? **Needs implementation** |
+| Auto-refresh timer | SignalR or polling | ?? **Needs implementation** |
+| Grid layout persistence | LocalStorage | ?? **Needs implementation** |
+| **frmEnvelopeEditor** | `/sender/envelope/{id}` | ? **Not implemented** |
+| ? **frmEnvelopeMainData** popup | Inline form section or stepper | ? **Not implemented** |
+| Document upload (Drag & Drop) | Blazor InputFile with drag zone | ?? **Needs implementation** |
+| Receiver grid (auto-complete) | DevExpress Blazor Grid with lookup | ?? **Needs implementation** |
+| Merge PDFs (frmOrderFiles) | Client-side PDF.js or server-side | ?? **Needs implementation** |
+| **frmFieldEditor** | `/sender/envelope/{id}/fields` or inline | ? **Not implemented** |
+| GdPicture PDF viewer | PDF.js + canvas overlay (like EnvelopeReceiverPage) | ?? **Partial (receiver side only)** |
+| Signature field placement | Drag & drop signature boxes on canvas | ? **Not implemented** |
+| Receiver color coding | CSS variables + signature field borders | ? **Not implemented** |
+| Multi-receiver switcher | Dropdown or tabs | ? **Not implemented** |
+| Thumbnail navigator | PDF.js thumbnail sidebar (like receiver) | ?? **Exists for receiver** |
+| Save signature fields | API POST `/api/Envelope/{id}/Elements` | ? **Not implemented** |
+| **frm2Factor_Properties** | Admin panel `/admin/2fa/{email}` | ? **Not implemented** |
+| **frmRueckruf** (Delete reason) | Modal dialog in EnvelopeSenderPage | ?? **Needs implementation** |
+
+---
+
+## Critical Implementation Notes
+
+### 1. **Coordinate System Consistency**
+**Database (Form App):** INCHES (GdPicture native)  
+**ReceiverUI (PDF.js):** Pixels on canvas  
+**Conversion Required:**
+```csharp
+// Sender side (placing fields):
+float xInches = canvasPixelX / (canvasWidth / pageWidthInches);
+float yInches = canvasPixelY / (canvasHeight / pageHeightInches);
+
+// Receiver side (displaying fields):
+float canvasX = (xInches / pageWidthInches) * canvasWidth;
+float canvasY = (yInches / pageHeightInches) * canvasHeight;
+```
+
+**A4 Page Dimensions:**
+- Width: 8.27" = 595pt
+- Height: 11.69" = 842pt
+
+---
+
+### 2. **Status Color System**
+Form app uses **DevExpress CustomDrawCell** event for row coloring. ReceiverUI should use:
+
+```css
+/* Envelope status colors */
+.envelope-row.status-partly-signed { background-color: #81C784; } /* GREEN_300 */
+.envelope-row.status-queued,
+.envelope-row.status-sent { background-color: #FFB74D; } /* ORANGE_300 */
+.envelope-row.status-completed { background-color: #81C784; } /* GREEN_300 */
+.envelope-row.status-deleted,
+.envelope-row.status-rejected { background-color: #E57373; } /* RED_300 */
+
+/* Receiver status colors */
+.receiver-row.signed { background-color: #81C784; }
+.receiver-row.unsigned { background-color: #E57373; }
+```
+
+---
+
+### 3. **Master-Detail Grid Pattern**
+Form app uses **nested GridViews** (ViewReceivers, ViewHistory). ReceiverUI options:
+
+**Option A:** DevExpress Blazor Grid with master-detail template
+```razor
+<DxGrid Data="@Envelopes">
+    <DxGridDataColumn FieldName="Title" />
+    <DxGridDetailRowTemplate>
+        <DxGrid Data="@context.EnvelopeReceivers">
+            <DxGridDataColumn FieldName="Name" />
+            <DxGridDataColumn FieldName="Status" />
+        </DxGrid>
+    </DxGridDetailRowTemplate>
+</DxGrid>
+```
+
+**Option B:** Click row ? show modal with receivers/history
+```razor
+<DxGrid @ref="grid" Data="@Envelopes" RowClick="OnRowClick">
+...
+</DxGrid>
+
+<DxPopup @bind-Visible="showDetailPopup">
+    <DxGrid Data="@selectedEnvelope.EnvelopeReceivers">
+    ...
+    </DxGrid>
+</DxPopup>
+```
+
+---
+
+### 4. **Signature Field Editor Architecture**
+
+**Form App:**
+- GdPicture14 native annotations
+- Fixed size (1.77×1.96 inches)
+- Color-coded per receiver
+- Draggable, non-resizable
+
+**ReceiverUI Equivalent:**
+- PDF.js canvas + HTML overlay (like receiver signature buttons)
+- `<div class="signature-field-placeholder">` positioned absolutely
+- Drag & drop with JS (`onmousedown`, `onmousemove`, `onmouseup`)
+- Snap to grid (optional)
+- Store coordinates in INCHES (convert from pixels)
+
+**Example HTML Overlay:**
+```html
+<div class="pdf-signature-layer">
+    <div class="signature-field" 
+         data-receiver-id="42" 
+         data-page="1"
+         style="position: absolute; left: 200px; top: 300px; width: 177px; height: 196px; background: rgba(255,0,0,0.3); border: 2px dashed red;">
+        Receiver: John Doe
+    </div>
+</div>
+```
+
+**JS Dragging Logic:**
+```javascript
+function makeSignatureFieldDraggable(element) {
+    let offsetX, offsetY;
+    element.onmousedown = (e) => {
+        offsetX = e.clientX - element.offsetLeft;
+        offsetY = e.clientY - element.offsetTop;
+        document.onmousemove = (e) => {
+            element.style.left = (e.clientX - offsetX) + 'px';
+            element.style.top = (e.clientY - offsetY) + 'px';
+        };
+        document.onmouseup = () => {
+            document.onmousemove = null;
+            saveFieldPosition(element); // Convert px ? inches ? API
+        };
+    };
+}
+```
+
+---
+
+### 5. **Auto-Complete Receiver Email**
+Form app uses **DevExpress ComboBox** with `AllReceiverEmails` list. ReceiverUI options:
+
+**Option A:** DevExpress Blazor TagBox with remote data
+```razor
+<DxTagBox Data="@previousEmails" 
+          @bind-Values="@selectedEmails"
+          AllowCustomTags="true"
+          ClearButtonDisplayMode="Auto">
+</DxTagBox>
+```
+
+**Option B:** HTML5 datalist
+```razor
+<input list="receiver-emails" @bind="newReceiverEmail" />
+<datalist id="receiver-emails">
+    @foreach (var email in previousEmails) {
+        <option value="@email" />
+    }
+</datalist>
+```
+
+---
+
+### 6. **Drag & Drop File Upload**
+Form app uses **WinForms DragDrop** events. ReceiverUI equivalent:
+
+```razor
+<div class="file-drop-zone" 
+     @ondragover="HandleDragOver" 
+     @ondragover:preventDefault 
+     @ondrop="HandleDrop" 
+     @ondrop:preventDefault>
+    <p>Drop PDF here or click to browse</p>
+    <InputFile OnChange="HandleFileSelected" accept=".pdf" />
+</div>
+
+@code {
+    async Task HandleDrop(DragEventArgs e) {
+        var files = e.DataTransfer.Files;
+        if (files.Length > 1) {
+            errorMessage = "Only one file allowed";
+            return;
+        }
+        await UploadDocument(files[0]);
+    }
+}
+```
+
+---
+
+### 7. **PDF Merge (frmOrderFiles)**
+Form app uses **GdPicture14 MergeDocuments**. ReceiverUI options:
+
+**Option A:** Server-side merge (iText7 or PDFSharp)
+```csharp
+[HttpPost("api/Document/Merge")]
+public async Task<IActionResult> MergePDFs([FromForm] List<IFormFile> files) {
+    using var outputStream = new MemoryStream();
+    using var pdfDocument = new PdfDocument(new PdfWriter(outputStream));
+    
+    foreach (var file in files) {
+        using var inputStream = file.OpenReadStream();
+        using var sourcePdf = new PdfDocument(new PdfReader(inputStream));
+        sourcePdf.CopyPagesTo(1, sourcePdf.GetNumberOfPages(), pdfDocument);
+    }
+    
+    pdfDocument.Close();
+    return File(outputStream.ToArray(), "application/pdf", "merged.pdf");
+}
+```
+
+**Option B:** Client-side merge (PDF-lib.js in Blazor JS interop)
+```javascript
+async function mergePDFs(fileDataUrls) {
+    const pdfDoc = await PDFDocument.create();
+    for (const dataUrl of fileDataUrls) {
+        const existingPdfBytes = await fetch(dataUrl).then(res => res.arrayBuffer());
+        const pdf = await PDFDocument.load(existingPdfBytes);
+        const copiedPages = await pdfDoc.copyPages(pdf, pdf.getPageIndices());
+        copiedPages.forEach(page => pdfDoc.addPage(page));
+    }
+    const pdfBytes = await pdfDoc.save();
+    return pdfBytes;
+}
+```
+
+---
+
+## Form App Workflow Summary
+
+### New Envelope Workflow (Sender)
+```
+1. Click "Create Envelope" in frmMain
+   ?
+2. frmEnvelopeMainData popup opens
+   - Enter Title (required)
+   - Select Envelope Type (loads defaults)
+   - Configure settings (Access Code, 2FA, Language, etc.)
+   - Click OK
+   ?
+3. frmEnvelopeEditor opens
+   - Add PDF document (drag & drop or browse)
+   - Add receivers (email auto-complete, access code auto-gen)
+   - Click "Edit Fields"
+   ?
+4. frmFieldEditor opens
+   - Select receiver from dropdown (colored circles)
+   - Click "Add Signature" ? draw box on PDF
+   - Drag to position (1.77×1.96 inches, fixed size)
+   - Repeat for each receiver
+   - Click "Save"
+   ?
+5. Back to frmEnvelopeEditor
+   - Click "Send Envelope"
+   - Validation:
+     * Title exists
+     * Message exists
+     * Document exists
+     * Receivers exist
+     * All receivers have signature fields
+   - Confirmation: "Do you want to start the signature process now?"
+   - Click Yes ? Envelope status = EnvelopeSent
+   ?
+6. Emails sent to receivers with invitation links
+   ?
+7. frmMain refreshes, envelope moves to "Sent" (orange color)
+```
+
+### Receiver Signing Workflow (External)
+```
+1. Receiver clicks link in email
+   ?
+2. Web browser opens (EnvelopeGenerator.Web or ReceiverUI)
+   - If UseAccessCode=true: Enter 6-digit code
+   - If TFA=true: Enter SMS code
+   ?
+3. PDF viewer loads with signature fields highlighted
+   - Click "Sign" button on each field
+   - Draw/type/upload signature
+   - Enter name, position, place
+   ?
+4. Submit ? Backend stamps signature on PDF
+   ?
+5. Envelope status updates:
+   - First signature ? EnvelopePartlySigned (green)
+   - Last signature ? EnvelopeCompletelySigned (green)
+   ?
+6. Final emails sent (if configured):
+   - To creator: "All receivers signed"
+   - To receivers: "Envelope completed, download PDF"
+```
+
+---
+
+## Missing Features in ReceiverUI (To Implement)
+
+### High Priority
+1. ? **Envelope list grid** (`/sender`) with status colors
+2. ? **Master-detail grids** (receivers/history)
+3. ? **Create/Edit envelope form** (`/sender/envelope/{id}`)
+4. ? **Envelope settings popup/stepper** (title, type, options)
+5. ? **Document upload** (drag & drop, single PDF)
+6. ? **Receiver management** (add/edit/delete with auto-complete)
+7. ? **Signature field editor** (PDF.js + draggable overlays)
+8. ? **Send envelope** (validation + API call)
+
+### Medium Priority
+9. ? **Delete envelope** (with reason modal)
+10. ? **Resend invitation** (per receiver)
+11. ? **Show document** (PDF preview)
+12. ? **Contact receiver** (mailto link)
+13. ? **Export to Excel** (grid data)
+14. ? **PDF merge tool** (multi-file select + merge)
+15. ? **Grid layout persistence** (LocalStorage)
+
+### Low Priority
+16. ? **2FA management** (admin panel)
+17. ? **Reports tab** (statistics, admin only)
+18. ? **Auto-refresh** (SignalR or polling)
+19. ? **Ghost mode** (impersonate user, admin only)
+20. ? **Log file export** (debug tool)
+
+---
+
+## Data Flow Diagram
+
+```
+????????????????????????
+?   frmMain            ?  ? Envelope list (Active/Completed tabs)
+?   (Dashboard)        ?  ? Status colors (Green/Orange/Red)
+????????????????????????  ? Master-detail grids (Receivers/History)
+          ?                ? Toolbar actions (Create/Edit/Delete/Send)
+          ? Click "Create"
+          ?
+????????????????????????
+? frmEnvelopeMainData  ?  ? Popup: Title, Type, Settings
+? (Settings Popup)     ?  ? Dropdowns: Language, Certification, Final Emails
+????????????????????????  ? Checkboxes: Access Code, 2FA, Reminders
+          ? Click OK
+          ?
+????????????????????????
+? frmEnvelopeEditor    ?  ? Document upload (drag & drop)
+? (Main Editor)        ?  ? Receiver grid (email auto-complete)
+????????????????????????  ? Merge PDFs button
+          ? Click "Edit Fields"
+          ?
+????????????????????????
+? frmFieldEditor       ?  ? GdPicture PDF viewer
+? (Signature Placer)   ?  ? Receiver selector (colored circles)
+????????????????????????  ? Draggable signature boxes (1.77×1.96")
+          ? Click "Save"
+          ?
+????????????????????????
+? Database             ?  ? DocReceiverElement (X, Y, Width, Height in INCHES)
+? (TBSIG_ELEMENT)      ?  ? EnvelopeReceiver (Name, Email, Access Code, Phone)
+????????????????????????  ? Envelope (Title, Status, Settings)
+          ? Click "Send Envelope"
+          ?
+????????????????????????
+? Email Service        ?  ? Send invitation emails to receivers
+?                      ?  ? Template: Link + Access Code (if enabled)
+????????????????????????
+          ?
+          ?
+????????????????????????
+? Receiver Web Page    ?  ? PDF.js viewer with signature buttons
+? (EnvelopeReceiverPage)? ? Click button ? Signature popup (draw/type/image)
+????????????????????????  ? Submit ? API stamps signature on PDF
+          ?
+          ?
+????????????????????????
+? Database Update      ?  ? EnvelopeHistory (Signed, Timestamp)
+?                      ?  ? Envelope Status ? PartlySigned / CompletelySigned
+????????????????????????
+          ? All signed?
+          ?
+????????????????????????
+? Final Email Service  ?  ? Send "Completed" email to creator/receivers
+?                      ?  ? Attach signed PDF
+????????????????????????
+```
+
+---
+
+## Key Takeaways for Migration
+
+1. **Tab-based layout** ? Single grid with status filter dropdown
+2. **Status colors** ? CSS classes or inline styles
+3. **Master-detail grids** ? Expandable rows or modal dialogs
+4. **Popup settings form** ? Inline form or stepper UI
+5. **GdPicture PDF viewer** ? PDF.js with canvas overlay
+6. **Signature field dragging** ? HTML5 drag & drop + absolute positioning
+7. **Coordinate system** ? **ALWAYS INCHES** in database, convert to/from pixels for UI
+8. **Receiver colors** ? CSS variables or inline styles
+9. **Auto-complete emails** ? DevExpress TagBox or HTML5 datalist
+10. **PDF merge** ? Server-side (iText7) or client-side (PDF-lib.js)
+
+---
+
+**Last Updated:** Session 20 (Form Application Analysis)