Refactor envelope receiver auth flow and state handling

- Introduce IReceiverAuthService and ReceiverAuthService for all envelope receiver authentication and status API calls
- Add ReceiverAuthModel as a client-side DTO for API responses
- Refactor EnvelopeState to store all relevant fields and update via ApplyApiResponse
- Overhaul EnvelopePage.razor to use new service and state, with improved status handling and UI
- Enhance ApiResponse and ApiServiceBase to support structured error deserialization
- Register IReceiverAuthService in DI container

EnvelopeGenerator.ReceiverUI/EnvelopeGenerator.ReceiverUI.Client/State/EnvelopeState.cs

@@ -1,4 +1,6 @@
-namespace EnvelopeGenerator.ReceiverUI.Client.State;
+using EnvelopeGenerator.ReceiverUI.Client.Models;
+
+namespace EnvelopeGenerator.ReceiverUI.Client.State;
 
 /// <summary>
 /// Hält den aktuellen Zustand des geladenen Umschlags.
@@ -9,11 +11,13 @@
 /// - StateHasChanged() informiert automatisch alle Subscriber
 /// 
 /// PATTERN: "Observable State" — Services setzen den State, Komponenten reagieren darauf.
+/// 
+/// Die Set-Methoden nehmen jetzt ein ReceiverAuthModel entgegen,
+/// damit alle Felder (Title, SenderEmail, TfaType etc.) zentral gespeichert werden.
 /// </summary>
 public class EnvelopeState
 {
     private EnvelopePageStatus _status = EnvelopePageStatus.Loading;
-    private string? _errorMessage;
 
     /// <summary>Aktueller Seitenstatus</summary>
     public EnvelopePageStatus Status
@@ -26,42 +30,87 @@ public class EnvelopeState
         }
     }
 
-    /// <summary>Fehlermeldung (falls vorhanden)</summary>
-    public string? ErrorMessage
-    {
-        get => _errorMessage;
-        private set
-        {
-            _errorMessage = value;
-            NotifyStateChanged();
-        }
-    }
+    // ── Felder aus ReceiverAuthModel ──
 
-    // --- Zustandsübergänge (öffentliche Methoden) ---
+    /// <summary>Titel des Umschlags (z.B. "Vertragsdokument")</summary>
+    public string? Title { get; private set; }
 
-    public void SetLoading() => Status = EnvelopePageStatus.Loading;
+    /// <summary>Nachricht des Absenders</summary>
+    public string? Message { get; private set; }
 
-    public void SetAccessCodeRequired()
+    /// <summary>E-Mail des Absenders (für Rückfragen-Hinweis)</summary>
+    public string? SenderEmail { get; private set; }
+
+    /// <summary>Ob TFA für diesen Umschlag aktiviert ist</summary>
+    public bool TfaEnabled { get; private set; }
+
+    /// <summary>Ob der Empfänger eine Telefonnummer hat (für SMS-TFA)</summary>
+    public bool HasPhoneNumber { get; private set; }
+
+    /// <summary>Ob das Dokument nur gelesen werden soll (ReadAndConfirm)</summary>
+    public bool ReadOnly { get; private set; }
+
+    /// <summary>TFA-Typ: "sms" oder "authenticator"</summary>
+    public string? TfaType { get; private set; }
+
+    /// <summary>Ablaufzeit des SMS-Codes (für Countdown-Timer)</summary>
+    public DateTime? TfaExpiration { get; private set; }
+
+    /// <summary>Fehlermeldung (z.B. "Falscher Zugangscode")</summary>
+    public string? ErrorMessage { get; private set; }
+
+    // ── Zustandsübergänge ──
+
+    public void SetLoading()
     {
         ErrorMessage = null;
-        Status = EnvelopePageStatus.RequiresAccessCode;
+        Status = EnvelopePageStatus.Loading;
     }
 
-    public void SetTwoFactorRequired() => Status = EnvelopePageStatus.RequiresTwoFactor;
+    /// <summary>
+    /// Setzt den State aus einer API-Antwort.
+    /// Zentrale Methode — alle Endpunkte liefern ReceiverAuthModel,
+    /// und diese Methode mappt den Status-String auf das richtige Enum.
+    /// </summary>
+    public void ApplyApiResponse(ReceiverAuthModel model)
+    {
+        // Gemeinsame Felder immer übernehmen
+        Title = model.Title ?? Title;
+        Message = model.Message ?? Message;
+        SenderEmail = model.SenderEmail ?? SenderEmail;
+        TfaEnabled = model.TfaEnabled;
+        HasPhoneNumber = model.HasPhoneNumber;
+        ReadOnly = model.ReadOnly;
+        TfaType = model.TfaType ?? TfaType;
+        TfaExpiration = model.TfaExpiration ?? TfaExpiration;
+        ErrorMessage = model.ErrorMessage;
 
-    public void SetDocument() => Status = EnvelopePageStatus.ShowDocument;
+        // Status-String → Enum
+        Status = model.Status switch
+        {
+            "requires_access_code" => EnvelopePageStatus.RequiresAccessCode,
+            "requires_tfa" => EnvelopePageStatus.RequiresTwoFactor,
+            "show_document" => EnvelopePageStatus.ShowDocument,
+            "already_signed" => EnvelopePageStatus.AlreadySigned,
+            "rejected" => EnvelopePageStatus.Rejected,
+            "not_found" => EnvelopePageStatus.NotFound,
+            "expired" => EnvelopePageStatus.Expired,
+            "error" => EnvelopePageStatus.Error,
+            _ => EnvelopePageStatus.Error
+        };
+    }
 
+    /// <summary>Setzt Fehler wenn der API-Call selbst fehlschlägt (Netzwerk etc.)</summary>
     public void SetError(string message)
     {
         ErrorMessage = message;
         Status = EnvelopePageStatus.Error;
     }
 
-    public void SetAlreadySigned() => Status = EnvelopePageStatus.AlreadySigned;
-    public void SetRejected() => Status = EnvelopePageStatus.Rejected;
+    /// <summary>Setzt NotFound (z.B. bei 404 ohne Body)</summary>
     public void SetNotFound() => Status = EnvelopePageStatus.NotFound;
 
-    // --- Event: Benachrichtigt Komponenten über Änderungen ---
+    // ── Event ──
     public event Action? OnChange;
     private void NotifyStateChanged() => OnChange?.Invoke();
 }