docs: document push token and firebase notification setup

android/CHANGELOG.md

@@ -679,3 +679,24 @@
   - add contact by email,
   - remove contact,
   - loading/refresh/error/info states.
+
+### Step 104 - Push token sync (Android + backend)
+- Added backend push token lifecycle API and storage:
+  - `POST /api/v1/notifications/push-token`
+  - `DELETE /api/v1/notifications/push-token`
+  - new table `push_device_tokens` (+ Alembic migration `0027_push_device_tokens`).
+- Added Android push token sync manager:
+  - registers FCM token on app start and after auth refresh/login,
+  - updates backend token on `FirebaseMessagingService.onNewToken`,
+  - unregisters token on logout.
+- Added backend FCM delivery in Celery notification tasks:
+  - sends to registered user device tokens,
+  - auto-removes invalid/unregistered tokens,
+  - safe fallback logs when Firebase is not configured.
+
+### Step 105 - Web Firebase push registration
+- Added web-side Firebase Messaging bootstrap (env-driven, no hardcoded secrets):
+  - fetch web push token and register in backend via `/notifications/push-token`,
+  - unregister token on logout,
+  - handle foreground push payload via existing notification service worker.
+- Added required env keys to `web/.env.example` and backend Firebase env keys to root `.env.example`.