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/20260121115517_AddStripeSubscriptionFields.cs

@@ -0,0 +1,69 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace TrueCV.Infrastructure.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddStripeSubscriptionFields : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<DateTime>(
+                name: "CurrentPeriodEnd",
+                table: "AspNetUsers",
+                type: "datetime2",
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "StripeSubscriptionId",
+                table: "AspNetUsers",
+                type: "nvarchar(256)",
+                maxLength: 256,
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SubscriptionStatus",
+                table: "AspNetUsers",
+                type: "nvarchar(32)",
+                maxLength: 32,
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Users_StripeCustomerId",
+                table: "AspNetUsers",
+                column: "StripeCustomerId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Users_StripeSubscriptionId",
+                table: "AspNetUsers",
+                column: "StripeSubscriptionId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Users_StripeCustomerId",
+                table: "AspNetUsers");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Users_StripeSubscriptionId",
+                table: "AspNetUsers");
+
+            migrationBuilder.DropColumn(
+                name: "CurrentPeriodEnd",
+                table: "AspNetUsers");
+
+            migrationBuilder.DropColumn(
+                name: "StripeSubscriptionId",
+                table: "AspNetUsers");
+
+            migrationBuilder.DropColumn(
+                name: "SubscriptionStatus",
+                table: "AspNetUsers");
+        }
+    }
+}