Add Swiss QR Code extraction feature

Introduced DTOs for request and response to handle Swiss QR Code extraction from PDF documents. Implemented `ExtractSwissQrCodeHandler` to process the extraction using `ISwissQrCodeProcessor`. Added validation for the query with `ExtractSwissQrCodeValidator`. Developed unit tests to ensure correct behavior for successful and failure scenarios.

DocumentOperator.Application/Features/Documents/ExtractSwissQrCode/ExtractSwissQrCodeHandler.cs

@@ -0,0 +1,33 @@
+using DocumentOperator.Application.Common.Interfaces;
+using MediatR;
+
+namespace DocumentOperator.Application.Features.Documents.ExtractSwissQrCode;
+
+/// <summary>
+/// Handles extraction of Swiss QR Code from PDF documents.
+/// Uses ISwissQrCodeProcessor to extract QR code from the last page and parse it.
+/// </summary>
+public sealed class ExtractSwissQrCodeHandler : IRequestHandler<ExtractSwissQrCodeQuery, ExtractSwissQrCodeResult>
+{
+    private readonly ISwissQrCodeProcessor _qrCodeProcessor;
+
+    public ExtractSwissQrCodeHandler(ISwissQrCodeProcessor qrCodeProcessor)
+    {
+        _qrCodeProcessor = qrCodeProcessor;
+    }
+
+    public async Task<ExtractSwissQrCodeResult> Handle(ExtractSwissQrCodeQuery request, CancellationToken cancellationToken)
+    {
+        // Convert Base64 string to byte array
+        byte[] pdfBytes = request.PdfContent.ToByteArray();
+
+        // Extract and parse Swiss QR Code from last page
+        var qrCodeData = await _qrCodeProcessor.ExtractSwissQrCodeAsync(pdfBytes, cancellationToken);
+
+        // Return references (passed through) + QR code data
+        return new ExtractSwissQrCodeResult(
+            References: request.References,
+            QrCodeData: qrCodeData
+        );
+    }
+}