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.Application/Helpers/ScoreThresholds.cs

@@ -0,0 +1,21 @@
+namespace TrueCV.Application.Helpers;
+
+public static class ScoreThresholds
+{
+    public const int High = 70;
+    public const int Medium = 50;
+
+    public static string GetScoreClass(int score) => score switch
+    {
+        > High => "score-high",
+        >= Medium => "score-medium",
+        _ => "score-low"
+    };
+
+    public static string GetBadgeClass(int score) => score switch
+    {
+        > High => "bg-success",
+        >= Medium => "bg-warning text-dark",
+        _ => "bg-danger"
+    };
+}