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.Domain/Entities/AuditLog.cs

@@ -0,0 +1,28 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace TrueCV.Domain.Entities;
+
+public class AuditLog
+{
+    [Key]
+    public Guid Id { get; set; }
+
+    public Guid UserId { get; set; }
+
+    [Required]
+    [MaxLength(64)]
+    public string Action { get; set; } = string.Empty;
+
+    [MaxLength(128)]
+    public string? EntityType { get; set; }
+
+    public Guid? EntityId { get; set; }
+
+    [MaxLength(1024)]
+    public string? Details { get; set; }
+
+    [MaxLength(64)]
+    public string? IpAddress { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+}