Initial commit: QR Scanner Flutter app

App móvil para validar pases QR contra base-admin-web con login Cognito,
escáner en tiempo real, feedback auditivo/háptico y README completo.

test/widget_test.dart

@@ -0,0 +1,13 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:qrscanner/main.dart';
+
+void main() {
+  testWidgets('Login screen renders correctly', (WidgetTester tester) async {
+    await tester.pumpWidget(const MyApp());
+
+    expect(find.text('QR Scanner'), findsOneWidget);
+    expect(find.text('Iniciar sesión'), findsOneWidget);
+    expect(find.text('Usuario'), findsOneWidget);
+  });
+}