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/ExtractSwissQrCodeQueryValidator.cs

@@ -5,55 +5,15 @@ namespace DocumentOperator.Application.SwissQrCode.Queries;
 
 /// <summary>
 /// Validates ExtractSwissQrCodeQuery before handler execution.
-/// Ensures exactly ONE input method is provided (either PdfBytes OR Base64Pdf, not both, not none).
+/// Ensures PdfStream is not null.
 /// </summary>
 public sealed class ExtractSwissQrCodeQueryValidator : AbstractValidator<ExtractSwissQrCodeQuery>
 {
     public ExtractSwissQrCodeQueryValidator()
     {
-        RuleFor(x => x)
-            .Must(HasExactlyOneInput)
-            .WithMessage("Either PdfBytes or Base64Pdf must be provided, but not both");
-
-        // Validate Base64 format if provided
-        When(x => !string.IsNullOrWhiteSpace(x.Base64Pdf), () =>
-        {
-            RuleFor(x => x.Base64Pdf)
-                .Must(BeValidBase64)
-                .WithMessage("Invalid Base64 format");
-        });
-
-        // Validate byte array if provided
-        When(x => x.PdfBytes != null, () =>
-        {
-            RuleFor(x => x.PdfBytes)
-                .NotEmpty()
-                .WithMessage("PdfBytes cannot be empty");
-        });
-    }
-
-    private static bool HasExactlyOneInput(ExtractSwissQrCodeQuery request)
-    {
-        var hasPdfBytes = request.PdfBytes != null && request.PdfBytes.Length > 0;
-        var hasBase64 = !string.IsNullOrWhiteSpace(request.Base64Pdf);
-
-        // XOR: exactly one must be true
-        return hasPdfBytes ^ hasBase64;
-    }
-
-    private static bool BeValidBase64(string? base64)
-    {
-        if (string.IsNullOrWhiteSpace(base64))
-            return false;
-
-        try
-        {
-            Convert.FromBase64String(base64);
-            return true;
-        }
-        catch (FormatException)
-        {
-            return false;
-        }
+        // Rule: PdfStream must be provided
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
     }
 }