Phase 3.1 WIP: Riverpod migration (client_app Auth + ChatOpening)

- Add phase3.1 requirement and implementation plan docs
- Add Riverpod dependencies to both client_app and mitra_app
- Wrap both app roots with ProviderScope
- Migrate client_app AuthBloc → AuthNotifier (@riverpod annotation)
- Migrate client_app ChatOpeningBloc → chatPricingProvider (FutureProvider)
- Update router to use Riverpod-based auth state for redirects
- Update all auth screens (display name, register, OTP, force register)
- Update home screen and pricing bottom sheet
- Add android:usesCleartextTraffic for dev HTTP access on both apps
- mitra_app prepared with ProviderScope + ApiClient provider (blocs next)

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

client_app/android/app/src/main/AndroidManifest.xml

@@ -2,7 +2,8 @@
     <application
         android:label="client_app"
         android:name="${applicationName}"
-        android:icon="@mipmap/ic_launcher">
+        android:icon="@mipmap/ic_launcher"
+        android:usesCleartextTraffic="true">
         <activity
             android:name=".MainActivity"
             android:exported="true"