feat: initialize Flutter project with version management

- Initialize Flutter 3.38 project with all platforms
- Add build-time version generation from pubspec.yaml
- Print version to console on app startup
- Create CHANGELOG.md following Keep a Changelog format
- Update .gitignore for Flutter + generated files
- Basic app scaffold with Material 3 theming

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/widget_test.dart

@@ -0,0 +1,12 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:tatlock_ui/main.dart';
+
+void main() {
+  testWidgets('App renders home page', (WidgetTester tester) async {
+    await tester.pumpWidget(const TatlockApp());
+
+    expect(find.text('Tatlock UI'), findsOneWidget);
+    expect(find.text('Welcome to Tatlock UI'), findsOneWidget);
+  });
+}