feat: Add Stripe payment integration and subscription management

- Add Stripe.net SDK for payment processing
- Implement StripeService with checkout sessions, customer portal, webhooks
- Implement SubscriptionService for quota management
- Add quota enforcement to CVCheckService
- Create Pricing, Billing, Settings pages
- Add checkout success/cancel pages
- Update Check and Dashboard with usage indicators
- Add ResetMonthlyUsageJob for billing cycle resets
- Add database migration for subscription fields

Plan tiers: Free (3 checks), Professional £49/mo (30), Enterprise £199/mo (unlimited)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/TrueCV.Infrastructure/Services/CVCheckService.cs

@@ -8,6 +8,7 @@ using TrueCV.Application.Interfaces;
 using TrueCV.Application.Models;
 using TrueCV.Domain.Entities;
 using TrueCV.Domain.Enums;
+using TrueCV.Domain.Exceptions;
 using TrueCV.Infrastructure.Data;
 using TrueCV.Infrastructure.Jobs;
 
@@ -19,6 +20,7 @@ public sealed class CVCheckService : ICVCheckService
     private readonly IFileStorageService _fileStorageService;
     private readonly IBackgroundJobClient _backgroundJobClient;
     private readonly IAuditService _auditService;
+    private readonly ISubscriptionService _subscriptionService;
     private readonly ILogger<CVCheckService> _logger;
 
     public CVCheckService(
@@ -26,12 +28,14 @@ public sealed class CVCheckService : ICVCheckService
         IFileStorageService fileStorageService,
         IBackgroundJobClient backgroundJobClient,
         IAuditService auditService,
+        ISubscriptionService subscriptionService,
         ILogger<CVCheckService> logger)
     {
         _dbContext = dbContext;
         _fileStorageService = fileStorageService;
         _backgroundJobClient = backgroundJobClient;
         _auditService = auditService;
+        _subscriptionService = subscriptionService;
         _logger = logger;
     }
 
@@ -42,6 +46,13 @@ public sealed class CVCheckService : ICVCheckService
 
         _logger.LogDebug("Creating CV check for user {UserId}, file: {FileName}", userId, fileName);
 
+        // Check quota before proceeding
+        if (!await _subscriptionService.CanPerformCheckAsync(userId))
+        {
+            _logger.LogWarning("User {UserId} quota exceeded - CV check denied", userId);
+            throw new QuotaExceededException();
+        }
+
         // Upload file to blob storage
         var blobUrl = await _fileStorageService.UploadAsync(file, fileName);
 
@@ -71,6 +82,9 @@ public sealed class CVCheckService : ICVCheckService
 
         await _auditService.LogAsync(userId, AuditActions.CVUploaded, "CVCheck", cvCheck.Id, $"File: {fileName}");
 
+        // Increment usage after successful creation
+        await _subscriptionService.IncrementUsageAsync(userId);
+
         return cvCheck.Id;
     }