feat: push notification system

[mohitgauniyal]

Notification Architecture

• Event-driven system — routes emit events, dispatcher handles delivery
• rules.ts — single file to change who gets notified and what message
• Adding new notification type = 3-4 lines across 3 files

Backend

• events/emitter.ts — all app event constants in one place
• notifications/rules.ts — notification rules for all event types
• notifications/dispatcher.ts — listens to events, sends notifications
• utils/expoPush.ts — Expo Push API with token cleanup and error handling
• complaints.ts — emits events instead of direct push calls

Mobile

• Device token registration working with EAS build
• Notification permission request on first login
• Foreground notification handler — shows banner when app is open
• Tap handler with deep link map — tapping notification navigates to correct screen
• navigationRef wired to NavigationContainer

EAS Setup

• Firebase Android configured via EAS secret
• FCM V1 service account key uploaded
• app.config.js with dynamic googleServicesFile
• Development build working on Android

Tests

• Jest mock for expo-server-sdk
• 188 tests passing