fix: address analysis issues - remove unused import, fix deprecated APIs, update test

test/widget_test.dart

@@ -0,0 +1,13 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:traccar_client/main.dart';
+
+void main() {
+  testWidgets('TraccarClientApp smoke test', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(const TraccarClientApp());
+
+    // Verify the app title is displayed
+    expect(find.text('Traccar Client'), findsOneWidget);
+  });
+}