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.

lib/main.dart

@@ -0,0 +1,21 @@
+import 'package:flutter/material.dart';
+import 'package:qrscanner/screens/login_screen.dart';
+import 'package:qrscanner/theme/app_theme.dart';
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'QR Scanner',
+      debugShowCheckedModeBanner: false,
+      theme: AppTheme.darkTheme,
+      home: const LoginScreen(),
+    );
+  }
+}