Refactor: Rename DocumentOperator to DocumentService

Updated project and solution files to rename and restructure
`DocumentOperator` to `DocumentService`. Modified project
references in `DocumentService.API.csproj`, `DocumentService.Application.csproj`,
and `DocumentService.Infrastructure.csproj` to reflect the new
naming convention. Updated `DocumentService.sln` to remove
old project references, add new ones, and adjust configuration
and nested project mappings accordingly. This change aligns
the project structure with the new naming convention.

DocumentService.Infrastructure/Services/QrCodeProcessing/DevExpressSwissQrCodeProcessor.cs

@@ -0,0 +1,165 @@
+using Codecrete.SwissQRBill.Generator;
+using DevExpress.Drawing;
+using DevExpress.Pdf;
+using DocumentService.Application.Common.Interfaces;
+using DocumentService.Domain.Common.Exceptions;
+using SkiaSharp;
+using SkiaSharp.QrCode;
+using System.Collections.Concurrent;
+
+namespace DocumentService.Infrastructure.Services.QrCodeProcessing;
+
+/// <summary>
+/// Swiss QR Code processor using DevExpress PDF API for image extraction,
+/// SkiaSharp.QrCode for QR decoding, and Codecrete.SwissQRBill.Generator for Swiss QR parsing.
+/// 
+/// Strategy:
+/// 1. Extract all embedded images from PDF using GetDXImages()
+/// 2. Try to decode QR code from each image using SkiaSharp.QrCode
+/// 3. Parse Swiss QR format with Codecrete library
+/// 4. Return both parsed Bill and raw QR text lines
+/// </summary>
+public sealed class DevExpressSwissQrCodeProcessor : ISwissQrCodeProcessor
+{
+
+    /// <inheritdoc />
+    public async Task<(Bill Bill, string[] RawLines)> ExtractSwissQrCodeAsync(
+        Stream pdfStream,
+        int[]? pageNumbers = null,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(pdfStream, nameof(pdfStream));
+        
+        if (pdfStream.Length == 0)
+            throw new ArgumentException("PDF stream is empty.", nameof(pdfStream));
+
+        // Defensive validation: Seekable streams must be at Position = 0
+        // Non-seekable streams (e.g., NetworkStream) are not checked
+        if (pdfStream.CanSeek && pdfStream.Position != 0)
+            throw new BadRequestException(null, new ArgumentException(
+                "PDF stream must be positioned at the beginning (Position = 0).",
+                nameof(pdfStream)));
+
+        using var pdfDocument = new PdfDocumentProcessor();
+        pdfDocument.LoadDocument(pdfStream);
+
+        if (pdfDocument.Document.Pages.Count == 0)
+            throw new ArgumentException("PDF document contains no pages.", nameof(pdfStream));
+
+        // Determine which pages to scan
+        int[] pagesToScan = DeterminePageNumbers(pdfDocument.Document.Pages.Count, pageNumbers);
+
+        // Extract all images from specified pages (no pre-filtering)
+        var allImages = new ConcurrentBag<(int pageNumber, DXBitmap image)>();
+
+        foreach (int pageNumber in pagesToScan)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            // Define area: entire page
+            var page = pdfDocument.Document.Pages[pageNumber - 1];
+            var area = new PdfDocumentArea(pageNumber,
+                new PdfRectangle(0, 0, page.CropBox.Width, page.CropBox.Height));
+
+            // Extract images from this page
+            var images = pdfDocument.GetDXImages(area);
+
+            foreach (var image in images)
+            {
+                // Collect ALL images - QRCodeDecoder will determine if it's a QR code
+                allImages.Add((pageNumber, image));
+            }
+        }
+
+        if (allImages.IsEmpty)
+            throw new NotFoundException($"No images found in pages: {string.Join(", ", pagesToScan)}");
+
+        // Parallel scan all images
+        var qrCodeTasks = allImages.Select(imageData =>
+            Task.Run(() =>
+            {
+                using (imageData.image)
+                {
+                    string? qrText = DecodeQrCodeFromImage(imageData.image);
+                    if (!string.IsNullOrEmpty(qrText))
+                    {
+                        try
+                        {
+                            // Parse with Codecrete
+                            var bill = QRBill.DecodeQrCodeText(qrText);
+
+                            // Split raw text into lines (handle both \r\n and \n)
+                            // Remove leading/trailing \r and \n from each line
+                            var rawLines = qrText
+                                .Split(["\r\n", "\n"], StringSplitOptions.None)
+                                .Select(line => line.Trim('\r', '\n'))
+                                .ToArray();
+
+                            return (success: true, bill, rawLines, imageData.pageNumber);
+                        }
+                        catch
+                        {
+                            // Not a valid Swiss QR Bill, ignore
+                            return (success: false, bill: (Bill?)null, rawLines: (string[]?)null, pageNumber: 0);
+                        }
+                    }
+                    return (success: false, bill: (Bill?)null, rawLines: (string[]?)null, pageNumber: 0);
+                }
+            }, cancellationToken)
+        ).ToList();
+
+        // Wait for all tasks and find first valid Swiss QR
+        var results = await Task.WhenAll(qrCodeTasks);
+        var validResult = results.FirstOrDefault(r => r.success);
+
+        if (validResult.success && validResult.bill != null)
+        {
+            return (validResult.bill, validResult.rawLines!);
+        }
+
+        throw new NotFoundException(
+            $"No valid Swiss QR Code found in {allImages.Count} images across pages: {string.Join(", ", pagesToScan)}.");
+    }
+
+    /// <summary>
+    /// Determines which pages to scan based on optional page numbers parameter.
+    /// Default: Last page first, then all pages in reverse order.
+    /// </summary>
+    private static int[] DeterminePageNumbers(int totalPages, int[]? pageNumbers)
+    {
+        if (pageNumbers != null && pageNumbers.Length > 0)
+        {
+            // Validate page numbers
+            foreach (int pageNum in pageNumbers)
+                if (pageNum < 1 || pageNum > totalPages)
+                    throw new ArgumentException(
+                        $"Invalid page number {pageNum}. Document has {totalPages} pages.",
+                        nameof(pageNumbers));
+            return pageNumbers;
+        }
+
+        // Default: Scan all pages, last page first (Swiss QR standard)
+        return [.. Enumerable.Range(1, totalPages).OrderByDescending(p => p)];
+    }
+
+    /// <summary>
+    /// Decodes QR code from a DXBitmap image using SkiaSharp.QrCode.
+    /// Converts DXBitmap to SKBitmap and attempts decoding.
+    /// </summary>
+    private static string? DecodeQrCodeFromImage(DXBitmap dxImage)
+    {
+        // Convert DXBitmap to SKBitmap via MemoryStream (PNG format)
+        using var ms = new MemoryStream();
+        dxImage.Save(ms, DXImageFormat.Png);
+        ms.Position = 0;
+
+        // Decode using SkiaSharp.QrCode
+        using var skBitmap = SKBitmap.Decode(ms);
+        if (skBitmap == null)
+            return null;
+
+        // TryDecode returns true if QR code found and decoded successfully
+        bool success = QRCodeDecoder.TryDecode(skBitmap, out var text, out _);
+        return success ? text : null;
+    }
+}

DocumentService.Infrastructure/Services/StringExtensions.cs

@@ -0,0 +1,16 @@
+using System.Xml.Serialization;
+
+namespace DocumentService.Infrastructure.Services;
+
+public static class StringExtensions
+{
+    public static T? DeserializeXml<T>(this string xmlText)
+    {
+        if (string.IsNullOrWhiteSpace(xmlText))
+            return default;
+
+        var serializer = new XmlSerializer(typeof(T));
+        using var reader = new StringReader(xmlText);
+        return (T?)serializer.Deserialize(reader);
+    }
+}