Add Android support with configurable server URL and location permissions

- Add shared_preferences for persisting server URL
- Add SettingsService and PlatformService
- Add server URL input field on non-web platforms
- Make ApiConfig baseUrl configurable at runtime
- Add Android location permissions (ACCESS_FINE/COURSE_LOCATION, INTERNET)
- Request location permission on login and map init
- Fix geo_id type: use String instead of int (UUID format)
- Align share_service with API spec: remove unique_id, use share_id only
- Fix watch endpoint response: last_update instead of created_at
- Add error handling with SnackBars for geo operations
- Wrap login screen in SingleChildScrollView for keyboard handling
- Update map tile layer with userAgentPackageName for OSM

test/widget_test.dart

@@ -9,22 +9,17 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:family_safety_frontend/main.dart';
+import 'package:family_safety_frontend/services/settings_service.dart';
 
 void main() {
-  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
-    // Build our app and trigger a frame.
-    await tester.pumpWidget(const MyApp());
-
-    // Verify that our counter starts at 0.
-    expect(find.text('0'), findsOneWidget);
-    expect(find.text('1'), findsNothing);
-
-    // Tap the '+' icon and trigger a frame.
-    await tester.tap(find.byIcon(Icons.add));
+  testWidgets('App loads login screen', (WidgetTester tester) async {
+    await tester.pumpWidget(MyApp(
+      settingsService: SettingsService(),
+    ));
     await tester.pump();
 
-    // Verify that our counter has incremented.
-    expect(find.text('0'), findsNothing);
-    expect(find.text('1'), findsOneWidget);
+    expect(find.text('Family Safety'), findsOneWidget);
+    expect(find.byType(TabBar), findsOneWidget);
+    expect(find.byType(ElevatedButton), findsOneWidget);
   });
 }