feat: add Flutter web frontend with authentication and recipe management features

flutter/lib/main.dart

@@ -0,0 +1,24 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'core/router/app_router.dart';
+
+void main() {
+  runApp(const ProviderScope(child: RecipeApp()));
+}
+
+class RecipeApp extends ConsumerWidget {
+  const RecipeApp({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final router = ref.watch(appRouterProvider);
+    return MaterialApp.router(
+      title: 'Recipe App',
+      theme: ThemeData(
+        colorScheme: ColorScheme.fromSeed(seedColor: Colors.green),
+        useMaterial3: true,
+      ),
+      routerConfig: router,
+    );
+  }
+}