feat: Implement Flutter mobile app MVP

Complete Flutter mobile app structure with:
- All data models (Account, Event, Player, Staff, Convocation, EventDetail, UserInfo)
- ApiService with Dio and Bearer token interceptor
- AuthService with OIDC via flutter_web_auth and deep links
- AuthProvider, ScheduleProvider, EventDetailProvider state management
- LoginScreen, ScheduleScreen with filters, EventDetailScreen
- Reusable widgets: EventCard, FilterDropdown, LoadingIndicator
- main.dart with MultiProvider and auth initialization
- AndroidManifest.xml and Info.plist deep link configuration for myice://callback

Connects to existing FastAPI backend for schedule, events, and auth.

myice_mobile/pubspec.yaml

@@ -0,0 +1,25 @@
+---
+name: myice_mobile
+description: Flutter mobile app for MyIce
+publish_to: 'none'
+version: 1.0.0+1
+
+environment:
+  sdk: '>=3.1.0 <4.0.0'
+
+dependencies:
+  flutter:
+    sdk: flutter
+  dio: ^5.4.0
+  provider: ^6.1.0
+  shared_preferences: ^2.2.0
+  flutter_web_auth: ^0.6.0
+  intl: ^0.19.0
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^3.0.0
+
+flutter:
+  uses-material-design: true