refactor: Enable DevicePreview in demo mode

- Enabled DevicePreview
- Show UI in different devices

Author: fulleni

lib/main.dart

@@ -21,7 +21,7 @@ void main() async {
   if (appConfig.environment == AppEnvironment.demo) {
     runApp(
       DevicePreview(
-        enabled: !kReleaseMode,
+        enabled: true,
         builder: (context) => appWidget,
         tools: const [DeviceSection()],