Framework (tech stack & key versions) Runtime: Expo SDK 54, React Native 0.81, React 19 Language: TypeScript Navigation: Expo Router (tabs) – no react-navigation boilerplate needed State: React hooks only (no Redux); custom hooks for Firebase data Backend: Firebase Web SDK v9 (modular) → Auth + Firestore Realtime: Firestore onSnapshot listeners merging alerts + incidents Notifications: expo-notifications (local/dev friendly; production push via EAS later) Location/Maps: expo-location + react-native-maps (Google Maps key from .env) Styling: RN StyleSheet (simple, performant), can add Tailwind/NW later if needed Config: app.config.ts (reads .env; wires credentials/ GoogleService files) Build mode: Managed (no android//ios/ checked in); EAS later for release Offline: Firestore IndexedDB persistence (best-effort)