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>

mitra_app/ios/Runner/Runner.entitlements

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>aps-environment</key>
+	<string>development</string>
+</dict>
+</plist>