add flutter example app test

client/flutter_ui/lib/main.dart

@@ -0,0 +1,53 @@
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:window_manager/window_manager.dart';
+
+import 'src/app_shell.dart';
+import 'src/daemon_client.dart';
+import 'src/desktop_integration.dart';
+
+Future<void> main(List<String> args) async {
+  WidgetsFlutterBinding.ensureInitialized();
+
+  final daemonAddr = _readFlag(args, 'daemon-addr') ?? _defaultDaemonAddr();
+  final fakeDaemon = args.contains('--fake-daemon');
+
+  await windowManager.ensureInitialized();
+  const windowOptions = WindowOptions(
+    size: Size(900, 640),
+    minimumSize: Size(720, 520),
+    center: true,
+    title: 'NetBird',
+  );
+  await windowManager.waitUntilReadyToShow(windowOptions, () async {
+    await windowManager.show();
+    await windowManager.focus();
+  });
+
+  final client = fakeDaemon
+      ? FakeDaemonClient(daemonAddr: daemonAddr)
+      : GrpcDaemonClient(daemonAddr: daemonAddr);
+
+  final integration = DesktopIntegration(client: client);
+  await integration.initialize();
+
+  runApp(NetBirdFlutterApp(client: client, integration: integration));
+}
+
+String? _readFlag(List<String> args, String name) {
+  final prefix = '--$name=';
+  for (final arg in args) {
+    if (arg.startsWith(prefix)) {
+      return arg.substring(prefix.length);
+    }
+  }
+  return null;
+}
+
+String _defaultDaemonAddr() {
+  if (Platform.isWindows) {
+    return 'tcp://127.0.0.1:41731';
+  }
+  return 'unix:///var/run/netbird.sock';
+}