chore: Flutter mobile app, CI, and dev tooling

- mobile/: Flutter/Dart merchant mobile app skeleton
- .github/: GitHub Actions CI workflows
- .dockerignore: exclude host node_modules from build context
- .cursorrules: Cursor IDE project rules
- .claude/: Claude Code project settings and launch config

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

mobile/meezi_pos/lib/main.dart

@@ -0,0 +1,25 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:meezi_pos/core/router/app_router.dart';
+
+void main() {
+  WidgetsFlutterBinding.ensureInitialized();
+  runApp(const ProviderScope(child: MeeziPosApp()));
+}
+
+class MeeziPosApp extends ConsumerWidget {
+  const MeeziPosApp({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final router = ref.watch(appRouterProvider);
+    return MaterialApp.router(
+      title: 'Meezi POS',
+      theme: ThemeData(
+        colorScheme: ColorScheme.fromSeed(seedColor: const Color(0xFF0F6E56)),
+        useMaterial3: true,
+      ),
+      routerConfig: router,
+    );
+  }
+}