show classname instead of teacher name in teacher timetable view

lib/api/demo/data/demo_capabilities.dart

@@ -12,6 +12,9 @@ class DemoCapabilities {
     pushNotifications: true,
     timetablePastDays: null,
     timetableFutureDays: null,
+    // Die Demo-Persona ist explizit Schüler — null hieße "Backend kennt das
+    // Feld nicht" (siehe CapabilitiesResponse.userType).
+    userType: 'STUDENT',
     loaded: true,
   );
 }