feat: add subscriptions feature capsule - M1 database schema and Stripe client (refs #55)

- Create 4 new tables: subscriptions, subscription_events, donations, tier_vehicle_selections
- Add StripeClient wrapper with createCustomer, createSubscription, cancelSubscription,
  updatePaymentMethod, createPaymentIntent, constructWebhookEvent methods
- Implement SubscriptionsRepository with full CRUD and mapRow case conversion
- Add domain types for all subscription entities
- Install stripe npm package v20.2.0

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

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

backend/package.json

@@ -18,45 +18,46 @@
     "type-check": "tsc --noEmit"
   },
   "dependencies": {
-    "pg": "^8.13.1",
-    "ioredis": "^5.4.2",
-    "@fastify/multipart": "^9.0.1",
-    "axios": "^1.7.9",
-    "opossum": "^8.0.0",
-    "winston": "^3.17.0",
-    "zod": "^3.24.1",
-    "js-yaml": "^4.1.0",
-    "fastify": "^5.2.0",
+    "@fastify/autoload": "^6.0.1",
     "@fastify/cors": "^11.2.0",
     "@fastify/helmet": "^13.0.2",
     "@fastify/jwt": "^10.0.0",
+    "@fastify/multipart": "^9.0.1",
     "@fastify/type-provider-typebox": "^6.1.0",
     "@sinclair/typebox": "^0.34.0",
-    "fastify-plugin": "^5.0.1",
-    "@fastify/autoload": "^6.0.1",
-    "get-jwks": "^11.0.3",
-    "file-type": "^16.5.4",
-    "resend": "^3.0.0",
-    "node-cron": "^3.0.3",
     "auth0": "^4.12.0",
-    "tar": "^7.4.3"
+    "axios": "^1.7.9",
+    "fastify": "^5.2.0",
+    "fastify-plugin": "^5.0.1",
+    "file-type": "^16.5.4",
+    "get-jwks": "^11.0.3",
+    "ioredis": "^5.4.2",
+    "js-yaml": "^4.1.0",
+    "node-cron": "^3.0.3",
+    "opossum": "^8.0.0",
+    "pg": "^8.13.1",
+    "resend": "^3.0.0",
+    "stripe": "^20.2.0",
+    "tar": "^7.4.3",
+    "winston": "^3.17.0",
+    "zod": "^3.24.1"
   },
   "devDependencies": {
-    "@types/node": "^22.0.0",
-    "@types/pg": "^8.10.9",
-    "@types/js-yaml": "^4.0.9",
-    "@types/node-cron": "^3.0.11",
-    "typescript": "^5.7.2",
-    "ts-node": "^10.9.1",
-    "nodemon": "^3.1.9",
-    "jest": "^29.7.0",
-    "@types/jest": "^29.5.10",
-    "ts-jest": "^29.1.1",
-    "supertest": "^7.1.4",
-    "@types/supertest": "^6.0.3",
-    "@types/opossum": "^8.0.0",
-    "eslint": "^9.17.0",
     "@eslint/js": "^9.17.0",
+    "@types/jest": "^29.5.10",
+    "@types/js-yaml": "^4.0.9",
+    "@types/node": "^22.0.0",
+    "@types/node-cron": "^3.0.11",
+    "@types/opossum": "^8.0.0",
+    "@types/pg": "^8.10.9",
+    "@types/supertest": "^6.0.3",
+    "eslint": "^9.17.0",
+    "jest": "^29.7.0",
+    "nodemon": "^3.1.9",
+    "supertest": "^7.1.4",
+    "ts-jest": "^29.1.1",
+    "ts-node": "^10.9.1",
+    "typescript": "^5.7.2",
     "typescript-eslint": "^8.18.1"
   }
 }