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`.
The `IPdfProcessor` interface was added to the `Application/Common/Interfaces/` directory. It includes the `ValidateAsync` method for validating PDFs and extracting metadata, with proper XML documentation and dependency on domain value objects.
Updated `ROADMAP.md` to mark Step 3.1 as completed, detailing the creation of the `IPdfProcessor` interface and its implementation status.
Removed the `<Folder Include="Common\Interfaces\" />` entry from `DocumentOperator.Application.csproj` to reflect the transition from a placeholder folder structure to actual implementation.
