Add UK education verification and security fixes

Features:
- Add UK institution recognition (170+ universities)
- Add diploma mill detection (100+ blacklisted institutions)
- Add education verification service with date plausibility checks
- Add local file storage option (no Azure required)
- Add default admin user seeding on startup
- Enhance Serilog logging with file output

Security fixes:
- Fix path traversal vulnerability in LocalFileStorageService
- Fix open redirect in login endpoint (use LocalRedirect)
- Fix password validation message (12 chars, not 6)
- Fix login to use HTTP POST endpoint (avoid Blazor cookie issues)

Code improvements:
- Add CancellationToken propagation to CV parser
- Add shared helpers (JsonDefaults, DateHelpers, ScoreThresholds)
- Add IUserContextService for user ID extraction
- Parallelized company verification in ProcessCVCheckJob
- Add 28 unit tests for education verification

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

src/TrueCV.Domain/Entities/CVCheck.cs

@@ -1,5 +1,4 @@
 using System.ComponentModel.DataAnnotations;
-using System.ComponentModel.DataAnnotations.Schema;
 using TrueCV.Domain.Enums;
 
 namespace TrueCV.Domain.Entities;
@@ -31,9 +30,5 @@ public class CVCheck
 
     public DateTime? CompletedAt { get; set; }
 
-    // Navigation properties
-    [ForeignKey(nameof(UserId))]
-    public User User { get; set; } = null!;
-
     public ICollection<CVFlag> Flags { get; set; } = new List<CVFlag>();
 }