Update syncDatabase function to remove setupAssociations call: Added comments to clarify that associations should be set by the caller to prevent AssociationError during synchronization.

backend/utils/syncDatabase.js

@@ -687,8 +687,8 @@ const syncDatabase = async () => {
             }
         }
 
-        console.log("Setting up associations...");
-        setupAssociations();
+        // Associations werden vom Aufrufer (z. B. server.js) vor dem Aufruf von syncDatabase() gesetzt.
+        // Kein setupAssociations() hier, sonst doppelter Aufruf → AssociationError (alias "rooms" etc.).
 
         console.log("Synchronizing models...");
         await syncModelsWithUpdates(models);