implemented a comprehensive client-side demo mode triggered by a "demo@" username prefix, serving curated fixture data for all app modules

lib/view/pages/talk/chat_list.dart

@@ -11,6 +11,7 @@ import '../../../state/app/modules/chat_list/bloc/chat_list_bloc.dart';
 import '../../../state/app/modules/chat_list/bloc/chat_list_state.dart';
 import '../../../state/app/modules/settings/bloc/settings_cubit.dart';
 import '../../../widget/confirm_dialog.dart';
+import '../../../widget/demo_restricted.dart';
 import '../../../widget/placeholder_view.dart';
 import 'join_chat.dart';
 import 'notification_permission_prompt.dart';
@@ -100,6 +101,7 @@ class _ChatListViewState extends State<_ChatListView> {
             heroTag: 'createChat',
             backgroundColor: Theme.of(context).primaryColor,
             onPressed: () {
+              if (guardDemoAction(context)) return;
               showSearch(context: context, delegate: JoinChat()).then((
                 username,
               ) {