iOS push notification setup for client_app and mitra_app

- Add Runner.entitlements with aps-environment capability
- Add UIBackgroundModes (remote-notification, fetch) to Info.plist
- Add CODE_SIGN_ENTITLEMENTS to Debug/Release/Profile build configs
- Add GoogleService-Info.plist for both apps
- Upgrade Firebase packages and web_socket_channel to fix CocoaPods conflict
- Set client_app Podfile iOS platform to 15.0
- Fix mitra_app Xcode bundle ID to match Firebase (com.halobestie.mitra)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client_app/pubspec.yaml

@@ -12,9 +12,9 @@ dependencies:
     sdk: flutter
 
   # Firebase
-  firebase_core: ^2.27.1
-  firebase_auth: ^4.18.0
-  firebase_messaging: ^14.7.15
+  firebase_core: ^3.12.1
+  firebase_auth: ^5.5.1
+  firebase_messaging: ^15.2.5
 
   # Social login
   google_sign_in: ^6.2.1
@@ -22,7 +22,7 @@ dependencies:
 
   # HTTP & WebSocket
   dio: ^5.4.3
-  web_socket_channel: ^2.4.5
+  web_socket_channel: ^3.0.3
 
   # State management
   flutter_riverpod: ^2.6.1