refactor(application): migrate all queries to Stream-based API

- Replace byte[] and Base64String with required Stream PdfStream
- Simplify validators: remove XOR/Base64 validation, only check NotNull
- Affected queries: ValidatePdfQuery, ValidatePdfAQuery, CheckPdfAttachmentsQuery, ExtractSwissQrCodeQuery
- Memory efficiency: direct stream usage, no intermediate byte[] copies

DocumentOperator.Application/SwissQrCode/Queries/ExtractSwissQrCodeQuery.cs

@@ -6,19 +6,14 @@ using MediatR;
 namespace DocumentOperator.Application.SwissQrCode.Queries;
 
 /// <summary>
-/// Query for extracting Swiss QR Code from PDF (supports both byte array and Base64 input)
+/// Query for extracting Swiss QR Code from PDF (Stream-based)
 /// </summary>
 public record ExtractSwissQrCodeQuery : IRequest<SwissQrCodeExtractionResult>
 {
     /// <summary>
-    /// PDF as byte array (direct upload)
+    /// PDF as stream (caller is responsible for disposal)
     /// </summary>
-    public byte[]? PdfBytes { get; init; }
-
-    /// <summary>
-    /// PDF as Base64 string (API clients)
-    /// </summary>
-    public string? Base64Pdf { get; init; }
+    public required Stream PdfStream { get; init; }
 }
 
 /// <summary>
@@ -34,11 +29,8 @@ public class ExtractSwissQrCodeQueryHandler(ISwissQrCodeProcessor qrCodeProcesso
     /// </summary>
     public async Task<SwissQrCodeExtractionResult> Handle(ExtractSwissQrCodeQuery request, CancellationToken cancellationToken)
     {
-        // Use byte[] if available, otherwise convert Base64
-        byte[] pdfBytes = request.PdfBytes ?? Convert.FromBase64String(request.Base64Pdf!);
-
-        // Extract: returns (Bill, RawLines)
-        var (bill, rawLines) = await qrCodeProcessor.ExtractSwissQrCodeAsync(pdfBytes, pageNumbers: null, cancellationToken);
+        // Extract: returns (Bill, RawLines) - pass stream directly
+        var (bill, rawLines) = await qrCodeProcessor.ExtractSwissQrCodeAsync(request.PdfStream, pageNumbers: null, cancellationToken);
 
         // Map Codecrete Bill to DTO using AutoMapper
         var billDto = mapper.Map<SwissQrBillDto>(bill);