feat: integrate Stripe payment with bugfixes and active timeout cancellation

- Add Stripe payment provider with Checkout Session flow
- Payment provider abstraction layer (EasyPay + Stripe unified interface)
- Stripe webhook with proper raw body handling and signature verification
- Frontend: Stripe button with URL validation, anti-duplicate click, noopener
- Active timeout cancellation: query platform before expiring, recover paid orders
- Singleton Stripe client, idempotency keys, Math.round for amounts
- Handle async_payment events, return null for unknown webhook events
- Set Checkout Session expires_at aligned with order timeout
- Add cancelPayment to provider interface (Stripe: sessions.expire, EasyPay: no-op)
- Enable stripe in frontend payment type list

tsconfig.json

@@ -22,13 +22,6 @@
       "@/*": ["./src/*"]
     }
   },
-  "include": [
-    "next-env.d.ts",
-    "**/*.ts",
-    "**/*.tsx",
-    ".next/types/**/*.ts",
-    ".next/dev/types/**/*.ts",
-    "**/*.mts"
-  ],
-  "exclude": ["node_modules", "third-party"]
+  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts", ".next/dev/types/**/*.ts", "**/*.mts"],
+  "exclude": ["node_modules", "third-party", "vendor"]
 }