API notif dan penambahan package firebase-admin

Add:
- src/app/api/mobile/notifications/
- src/lib/firebase-admin.ts

### No Issue

package.json

@@ -61,6 +61,7 @@
     "echarts-for-react": "^3.0.2",
     "embla-carousel-react": "^8.0.0-rc14",
     "eslint-config-next": "^13.5.4",
+    "firebase-admin": "^13.6.0",
     "iron-session": "^6.3.1",
     "jose": "^5.9.2",
     "jotai": "^2.4.3",