fixing android build

lib/browser.dart

@@ -0,0 +1,14 @@
+/// Platform-aware browser API abstraction.
+///
+/// On web, provides real browser localStorage and location APIs.
+/// On non-web platforms (Android, iOS, desktop), returns no-op stubs.
+///
+/// Usage:
+/// ```dart
+/// import 'package:qpay/browser.dart';
+/// Browser.localStorage.setItem('key', 'value');
+/// Browser.localStorage.getItem('key');
+/// Browser.location.href = 'https://example.com';
+/// ```
+export 'platform/browser_stub.dart'
+    if (dart.library.html) 'platform/browser_web.dart';