Add service worker implementation and tests for PWA caching strategy

- Implemented a service worker (sw.js) that handles installation, activation, and fetch events.
- Added caching logic for public assets and a fallback for offline navigation.
- Created unit tests (sw.test.ts) to validate service worker behavior, including asset caching, navigation handling, and activation logic.
- Ensured that private API routes and third-party requests are excluded from caching.

package.json

@@ -14,6 +14,7 @@
     "db:migrate:production": "NODE_ENV=production bun --env-file=.env --env-file=.env.production scripts/migrate.ts",
     "test:coverage": "bun test --coverage",
     "test:smoke": "bun run build && bun scripts/api-smoke.ts",
+    "test:pwa": "bun run build && bun scripts/pwa-smoke.ts",
     "db:backup": "NODE_ENV=production bun --env-file=.env --env-file=.env.production scripts/backup.ts",
     "db:restore": "bun scripts/restore.ts",
     "monitor": "bun --env-file=.env --env-file=.env.production scripts/monitor.ts"
@@ -40,6 +41,7 @@
     "@types/react-dom": "^19",
     "drizzle-kit": "^0.31.10",
     "happy-dom": "^20.14.0",
+    "playwright": "^1.63.0",
     "tailwindcss": "^4.1.11",
     "typescript": "^7.0.2"
   }