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

lib/state/app/modules/chat_list/data_provider/chat_list_data_provider.dart

@@ -1,3 +1,5 @@
+import '../../../../../api/demo/data/demo_talk.dart';
+import '../../../../../api/demo/demo_mode.dart';
 import '../../../../../api/marianumcloud/talk/create_room/create_room.dart';
 import '../../../../../api/marianumcloud/talk/create_room/create_room_params.dart';
 import '../../../../../api/marianumcloud/talk/room/get_room_cache.dart';
@@ -8,13 +10,18 @@ class ChatListDataProvider {
   Future<GetRoomResponse> getRooms({
     void Function(Object)? onError,
     bool renew = false,
-  }) => resolveFromCache<GetRoomResponse>(
-    (onUpdate, onError) =>
-        GetRoomCache(renew: renew, onUpdate: onUpdate, onError: onError),
-    onError: onError,
-    operationName: 'getRooms',
-  );
+  }) {
+    if (DemoMode.active) return Future.value(DemoTalk.rooms());
+    return resolveFromCache<GetRoomResponse>(
+      (onUpdate, onError) =>
+          GetRoomCache(renew: renew, onUpdate: onUpdate, onError: onError),
+      onError: onError,
+      operationName: 'getRooms',
+    );
+  }
 
-  Future<void> createDirectRoom(String invite) =>
-      CreateRoom(CreateRoomParams(roomType: 1, invite: invite)).run();
+  Future<void> createDirectRoom(String invite) {
+    if (DemoMode.active) return Future.value();
+    return CreateRoom(CreateRoomParams(roomType: 1, invite: invite)).run();
+  }
 }