feat(quality): Sprint 2 pre-deploy gates and server smoke tests

Extract Express app factory for testability, add Vitest/Supertest API
smoke tests, root npm run check script, and deployment docs. Fix
express-rate-limit IPv6 keyGenerator for feedback limiter.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/package.json

@@ -7,7 +7,9 @@
   "scripts": {
     "build": "tsc",
     "start": "node dist/index.js",
-    "dev": "tsx watch src/index.ts"
+    "dev": "tsx watch src/index.ts",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "@prisma/client": "^5.10.2",
@@ -26,8 +28,11 @@
     "@types/cors": "^2.8.17",
     "@types/express": "^4.17.21",
     "@types/node": "^20.11.24",
+    "@types/supertest": "^6.0.3",
     "@types/web-push": "^3.6.4",
+    "supertest": "^7.1.0",
     "tsx": "^4.7.1",
-    "typescript": "^5.3.3"
+    "typescript": "^5.3.3",
+    "vitest": "^3.0.9"
   }
 }