chore(01-01): scaffold Flutter project with all dependencies and tooling

- Flutter project created with flutter create (Android platform)
- Runtime deps: flutter_riverpod, riverpod_annotation, drift 2.31, drift_flutter, go_router, path_provider, shared_preferences, flutter_localizations, intl
- Dev deps: riverpod_generator, drift_dev 2.31, build_runner
- Pinned drift/drift_dev to 2.31 for analyzer ^9.0.0 compatibility with riverpod_generator
- Configured l10n.yaml, build.yaml (Drift), analysis_options.yaml (riverpod_lint)
- Minimal ARB file for localization tooling to resolve

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

test/widget_test.dart

@@ -0,0 +1,30 @@
+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility in the flutter_test package. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:household_keeper/main.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));
+    await tester.pump();
+
+    // Verify that our counter has incremented.
+    expect(find.text('0'), findsNothing);
+    expect(find.text('1'), findsOneWidget);
+  });
+}