Add audit logging, processing stages, delete functionality, and bug fixes

- Add audit logging system for tracking CV uploads, processing, deletion,
  report views, and PDF exports for billing/reference purposes
- Add processing stage display on dashboard instead of generic "Processing"
- Add delete button for CV checks on dashboard
- Fix duplicate primary key error in CompanyCache (race condition)
- Fix DbContext concurrency in Dashboard (concurrent delete/load operations)
- Fix ProcessCVCheckJob to handle deleted records gracefully
- Fix duplicate flags in verification report by deduplicating on Title+Description
- Remove internal cache notes from verification results
- Add EF migrations for ProcessingStage and AuditLog table

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/TrueCV.Application/Interfaces/ICVCheckService.cs

@@ -10,4 +10,5 @@ public interface ICVCheckService
     Task<CVCheckDto?> GetCheckForUserAsync(Guid id, Guid userId);
     Task<List<CVCheckDto>> GetUserChecksAsync(Guid userId);
     Task<VeracityReport?> GetReportAsync(Guid checkId, Guid userId);
+    Task<bool> DeleteCheckAsync(Guid checkId, Guid userId);
 }