- Replace Firebase Auth with JWT stored in SharedPreferences
- Replace Firestore with REST API calls via new ApiService
- Replace Firebase Storage with POST /storage/upload
- Remove firebase_auth, firebase_core, cloud_firestore,
firebase_storage, firebase_messaging, google_sign_in deps
- Add api_service.dart as central HTTP client
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>