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.Infrastructure/DependencyInjection.cs

@@ -95,6 +95,7 @@ public static class DependencyInjection
         services.AddScoped<ITimelineAnalyserService, TimelineAnalyserService>();
         services.AddScoped<ICVCheckService, CVCheckService>();
         services.AddScoped<IUserContextService, UserContextService>();
+        services.AddScoped<IAuditService, AuditService>();
 
         // Register file storage - use local storage if configured, otherwise Azure
         var useLocalStorage = configuration.GetValue<bool>("UseLocalStorage");