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/Data/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -351,6 +351,9 @@ namespace TrueCV.Infrastructure.Data.Migrations
                         .IsConcurrencyToken()
                         .HasColumnType("nvarchar(max)");
 
+                    b.Property<DateTime?>("CurrentPeriodEnd")
+                        .HasColumnType("datetime2");
+
                     b.Property<string>("Email")
                         .HasMaxLength(256)
                         .HasColumnType("nvarchar(256)");
@@ -393,6 +396,14 @@ namespace TrueCV.Infrastructure.Data.Migrations
                         .HasMaxLength(256)
                         .HasColumnType("nvarchar(256)");
 
+                    b.Property<string>("StripeSubscriptionId")
+                        .HasMaxLength(256)
+                        .HasColumnType("nvarchar(256)");
+
+                    b.Property<string>("SubscriptionStatus")
+                        .HasMaxLength(32)
+                        .HasColumnType("nvarchar(32)");
+
                     b.Property<bool>("TwoFactorEnabled")
                         .HasColumnType("bit");
 
@@ -410,6 +421,12 @@ namespace TrueCV.Infrastructure.Data.Migrations
                         .HasDatabaseName("UserNameIndex")
                         .HasFilter("[NormalizedUserName] IS NOT NULL");
 
+                    b.HasIndex("StripeCustomerId")
+                        .HasDatabaseName("IX_Users_StripeCustomerId");
+
+                    b.HasIndex("StripeSubscriptionId")
+                        .HasDatabaseName("IX_Users_StripeSubscriptionId");
+
                     b.ToTable("AspNetUsers", (string)null);
                 });