Complete Step 1.1: ValidatePDF Application Layer

Updated PHASENPLAN and ROADMAP to reflect progress on Feature 1 - ValidatePDF (75% complete). Marked Step 1.1 as completed, including MediatR setup, pipeline behaviors (`ValidationBehavior`, `LoggingBehavior`), ValidatePDF feature (Query, Handler, Validator), and DTOs.

Added `DependencyInjection.cs` for Application Layer DI configuration. Introduced `LoggingBehavior` and `ValidationBehavior` for MediatR pipelines. Implemented `ValidatePdfHandler`, `ValidatePdfQuery`, and `ValidatePdfValidator`.

Created DTOs (`ValidatePdfRequest`, `ValidatePdfResponse`) for the ValidatePDF feature. Added unit tests for `ValidatePdfHandler` to verify metadata handling and exception propagation.

Removed unused folder references in `DocumentOperator.Application.csproj`.

DocumentOperator.Application/Common/DTOs/ValidatePdfRequest.cs

@@ -0,0 +1,7 @@
+namespace DocumentOperator.Application.Common.DTOs;
+
+/// <summary>
+/// Request DTO for ValidatePdf endpoint
+/// </summary>
+/// <param name="Base64Pdf">PDF content as Base64 string</param>
+public record ValidatePdfRequest(string Base64Pdf);

DocumentOperator.Application/Common/DTOs/ValidatePdfResponse.cs

@@ -0,0 +1,14 @@
+namespace DocumentOperator.Application.Common.DTOs;
+
+/// <summary>
+/// Response DTO for ValidatePdf endpoint
+/// Contains PDF metadata
+/// </summary>
+public record ValidatePdfResponse(
+    int PageCount,
+    long FileSizeBytes,
+    double FileSizeMB,
+    string PdfVersion,
+    bool HasAttachments,
+    int AttachmentCount
+);