refactor: Update Application handlers to convert byte[] to Stream

- ValidatePdfQueryHandler: Convert byte[] → MemoryStream before calling IPdfProcessor
- ValidatePdfAQueryHandler: Same pattern
- Update AutoMapper namespace imports (remove Domain.Models.ValueObjects references)

DocumentOperator.Application/ValidatePdf/Queries/ValidatePdfQuery.cs

@@ -36,10 +36,13 @@ public class ValidatePdfQueryHandler(IPdfProcessor PdfProcessor, IMapper Mapper)
         // Use byte[] if available, otherwise convert Base64
         byte[] pdfBytes = request.PdfBytes ?? Convert.FromBase64String(request.Base64Pdf!);
 
-        // Call DevExpress service (can throw PdfProcessingException)
-        var metadata = await PdfProcessor.ValidateAsync(pdfBytes);
+        // Convert to stream for IPdfProcessor (using MemoryStream)
+        using var pdfStream = new MemoryStream(pdfBytes);
 
-        // Map domain entity to DTO using AutoMapper
+        // Call DevExpress service (exceptions propagate naturally)
+        var metadata = await PdfProcessor.ValidateAsync(pdfStream);
+
+        // Map DTO to response DTO using AutoMapper
         return Mapper.Map<PdfValidationResult>(metadata);
     }
 }