fix(build): remove next-pwa and fix type errors

- Remove unused next-pwa dependency to eliminate workbox/rimraf warnings
- Fix DraftRecord type error by removing invalid updatedAt property
- Fix LLMService.getTeacherResponseStream type by adding optional onIntent callback

package.json

@@ -27,7 +27,6 @@
     "dexie-react-hooks": "^4.2.0",
     "lucide-react": "^0.562.0",
     "next": "16.1.4",
-    "next-pwa": "^5.6.0",
     "next-themes": "^0.4.6",
     "react": "19.2.3",
     "react-dom": "19.2.3",