Implement code review fixes and improvements

- Move admin credentials from hardcoded values to configuration
- Add rate limiting (5/min) to login endpoint for brute force protection
- Extract CleanJsonResponse to shared JsonResponseHelper class
- Add DateHelpers.MonthsBetween utility and consolidate date calculations
- Update PdfReportService to use ScoreThresholds constants
- Remove 5 unused shared components (EmploymentTable, FlagsList, etc.)
- Clean up unused CSS from MainLayout.razor.css
- Create IPdfReportService interface for better testability
- Add authentication requirement to Hangfire dashboard in development
- Seal EducationVerifierService class

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

src/TrueCV.Infrastructure/Services/AICompanyNameMatcherService.cs

@@ -7,6 +7,7 @@ using TrueCV.Application.Helpers;
 using TrueCV.Application.Interfaces;
 using TrueCV.Application.Models;
 using TrueCV.Infrastructure.Configuration;
+using TrueCV.Infrastructure.Helpers;
 
 namespace TrueCV.Infrastructure.Services;
 
@@ -112,7 +113,7 @@ public sealed class AICompanyNameMatcherService : ICompanyNameMatcherService
                 return null;
             }
 
-            responseText = CleanJsonResponse(responseText);
+            responseText = JsonResponseHelper.CleanJsonResponse(responseText);
 
             var aiResponse = JsonSerializer.Deserialize<AIMatchResponse>(responseText, JsonDefaults.CamelCase);
 
@@ -163,25 +164,4 @@ public sealed class AICompanyNameMatcherService : ICompanyNameMatcherService
             return null; // Fall back to fuzzy matching
         }
     }
-
-    private static string CleanJsonResponse(string response)
-    {
-        var trimmed = response.Trim();
-
-        if (trimmed.StartsWith("```json", StringComparison.OrdinalIgnoreCase))
-        {
-            trimmed = trimmed[7..];
-        }
-        else if (trimmed.StartsWith("```"))
-        {
-            trimmed = trimmed[3..];
-        }
-
-        if (trimmed.EndsWith("```"))
-        {
-            trimmed = trimmed[..^3];
-        }
-
-        return trimmed.Trim();
-    }
 }