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.Infrastructure/Services/CompanyVerifierService.cs

@@ -2,6 +2,7 @@ using FuzzySharp;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using TrueCV.Application.DTOs;
+using TrueCV.Application.Helpers;
 using TrueCV.Application.Interfaces;
 using TrueCV.Application.Models;
 using TrueCV.Domain.Entities;
@@ -113,7 +114,7 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
             CompanyNumber = item.CompanyNumber,
             CompanyName = item.Title,
             CompanyStatus = item.CompanyStatus ?? "Unknown",
-            IncorporationDate = ParseDate(item.DateOfCreation),
+            IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation),
             AddressSnippet = item.AddressSnippet
         }).ToList();
     }
@@ -166,8 +167,8 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
         {
             existingCache.CompanyName = item.Title;
             existingCache.Status = item.CompanyStatus ?? "Unknown";
-            existingCache.IncorporationDate = ParseDate(item.DateOfCreation);
-            existingCache.DissolutionDate = ParseDate(item.DateOfCessation);
+            existingCache.IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation);
+            existingCache.DissolutionDate = DateHelpers.ParseDate(item.DateOfCessation);
             existingCache.CachedAt = DateTime.UtcNow;
         }
         else
@@ -177,8 +178,8 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
                 CompanyNumber = item.CompanyNumber,
                 CompanyName = item.Title,
                 Status = item.CompanyStatus ?? "Unknown",
-                IncorporationDate = ParseDate(item.DateOfCreation),
-                DissolutionDate = ParseDate(item.DateOfCessation),
+                IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation),
+                DissolutionDate = DateHelpers.ParseDate(item.DateOfCessation),
                 CachedAt = DateTime.UtcNow
             };
 
@@ -230,18 +231,4 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
         };
     }
 
-    private static DateOnly? ParseDate(string? dateString)
-    {
-        if (string.IsNullOrWhiteSpace(dateString))
-        {
-            return null;
-        }
-
-        if (DateOnly.TryParse(dateString, out var date))
-        {
-            return date;
-        }
-
-        return null;
-    }
 }