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/CheckPdfAttachments/Queries/CheckPdfAttachmentsQueryValidator.cs

@@ -4,41 +4,15 @@ namespace DocumentOperator.Application.CheckPdfAttachments.Queries;
 
 /// <summary>
 /// Validator for CheckPdfAttachmentsQuery
-/// Ensures exactly one input type (PdfBytes OR Base64Pdf) is provided
+/// Ensures PdfStream is not null
 /// </summary>
 public class CheckPdfAttachmentsQueryValidator : AbstractValidator<CheckPdfAttachmentsQuery>
 {
     public CheckPdfAttachmentsQueryValidator()
     {
-        // Rule 1: Exactly ONE input must be provided (XOR logic)
-        RuleFor(x => x)
-            .Must(x => (x.PdfBytes != null && x.PdfBytes.Length > 0) ^
-                       (!string.IsNullOrWhiteSpace(x.Base64Pdf)))
-            .WithMessage("Either PdfBytes or Base64Pdf must be provided, but not both");
-
-        // Rule 2: Base64 format validation (if provided)
-        RuleFor(x => x.Base64Pdf)
-            .Must(BeValidBase64)
-            .When(x => !string.IsNullOrWhiteSpace(x.Base64Pdf))
-            .WithMessage("Base64Pdf must be a valid Base64 string");
-    }
-
-    /// <summary>
-    /// Validates if a string is a valid Base64 format
-    /// </summary>
-    private bool BeValidBase64(string? base64)
-    {
-        if (string.IsNullOrWhiteSpace(base64))
-            return true; // Skip validation if null/empty (handled by Rule 1)
-
-        try
-        {
-            Convert.FromBase64String(base64);
-            return true;
-        }
-        catch (FormatException)
-        {
-            return false;
-        }
+        // Rule: PdfStream must be provided and non-empty
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PdfStream is required");
     }
 }