refactor: Change IPdfProcessor interface from byte[] to Stream

- ValidateAsync(byte[]) → ValidateAsync(Stream)
- ValidatePdfAAsync(byte[]) → ValidatePdfAAsync(Stream)
- CheckAttachmentsAsync(byte[]) → CheckAttachmentsAsync(Stream)
- Reason: Stream-based processing reduces memory footprint and enables pipeline parallelization

DocumentOperator.Application/Common/Interfaces/IPdfProcessor.cs

@@ -1,4 +1,4 @@
-using DocumentOperator.Domain.Models.ValueObjects;
+using DocumentOperator.Application.Common.DTOs;
 
 namespace DocumentOperator.Application.Common.Interfaces;
 
@@ -7,20 +7,30 @@ public interface IPdfProcessor
     /// <summary>
     /// Validates a PDF and extracts metadata.
     /// </summary>
-    /// <param name="pdfBytes">PDF content as byte array</param>
+    /// <param name="pdfStream">PDF content as stream (caller is responsible for disposal)</param>
     /// <returns>PDF metadata (page count, size, version, attachments)</returns>
-    /// <exception cref="Domain.Common.Exceptions.PdfProcessingException">
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
-    /// Thrown when PDF is corrupted or cannot be processed
+    /// Thrown when stream is empty or invalid
     /// </exception>
-    Task<PdfMetadata> ValidateAsync(byte[] pdfBytes);
+    Task<PdfMetadata> ValidateAsync(Stream pdfStream);
 
     /// <summary>
     /// Validates a PDF/A document and checks conformance level.
     /// </summary>
-    /// <param name="pdfBytes">PDF content as byte array</param>
+    /// <param name="pdfStream">PDF content as stream (caller is responsible for disposal)</param>
     /// <returns>PDF/A metadata including conformance level and validation errors/warnings</returns>
-    /// <exception cref="Domain.Common.Exceptions.PdfProcessingException">
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
-    /// Thrown when PDF is corrupted or cannot be processed
+    /// Thrown when stream is empty or invalid
     /// </exception>
-    Task<PdfAMetadata> ValidatePdfAAsync(byte[] pdfBytes);
+    Task<PdfAMetadata> ValidatePdfAAsync(Stream pdfStream);
+
+    /// <summary>
+    /// Checks for embedded files (attachments) in a PDF document and returns detailed metadata.
+    /// </summary>
+    /// <param name="pdfStream">PDF content as stream (caller is responsible for disposal)</param>
+    /// <returns>Attachment information (count, file names, MIME types, sizes)</returns>
+    /// <exception cref="Domain.Common.Exceptions.BadRequestException">
+    /// Thrown when stream is empty or invalid
+    /// </exception>
+    Task<AttachmentInfo> CheckAttachmentsAsync(Stream pdfStream);
 }