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/Data/Migrations/20260120194532_AddAuditLogTable.cs

@@ -0,0 +1,55 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace TrueCV.Infrastructure.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddAuditLogTable : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "AuditLogs",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uniqueidentifier", nullable: false),
+                    UserId = table.Column<Guid>(type: "uniqueidentifier", nullable: false),
+                    Action = table.Column<string>(type: "nvarchar(64)", maxLength: 64, nullable: false),
+                    EntityType = table.Column<string>(type: "nvarchar(128)", maxLength: 128, nullable: true),
+                    EntityId = table.Column<Guid>(type: "uniqueidentifier", nullable: true),
+                    Details = table.Column<string>(type: "nvarchar(1024)", maxLength: 1024, nullable: true),
+                    IpAddress = table.Column<string>(type: "nvarchar(64)", maxLength: 64, nullable: true),
+                    CreatedAt = table.Column<DateTime>(type: "datetime2", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_AuditLogs", x => x.Id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_AuditLogs_Action",
+                table: "AuditLogs",
+                column: "Action");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_AuditLogs_CreatedAt",
+                table: "AuditLogs",
+                column: "CreatedAt");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_AuditLogs_UserId",
+                table: "AuditLogs",
+                column: "UserId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "AuditLogs");
+        }
+    }
+}