Initial commit: Fabled Android app

Flutter Android client for FabledAssistant with:
- Session-cookie auth via persistent cookie jar (Dio + cookie_jar)
- OAuth/SSO login via in-app WebView (flutter_inappwebview)
- Notes: list, detail (markdown render), create/edit
- Tasks: list with status tabs, create/edit with priority
- Chat: SSE streaming bubbles, conversation management
- Quick Capture FAB for rapid note/task creation
- Settings screen (change server URL, logout)
- Android home screen widget → opens chat
- Riverpod state management, go_router navigation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/widget_test.dart

@@ -0,0 +1,8 @@
+// Placeholder — integration tests go here once the app is running on device.
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  test('placeholder', () {
+    expect(true, isTrue);
+  });
+}