show classname instead of teacher name in teacher timetable view

lib/view/pages/timetable/data/lesson_merger.dart

@@ -1,3 +1,5 @@
+import 'package:flutter/foundation.dart';
+
 import '../../../../api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
 
 /// Combines back-to-back lessons with identical subject/room/teacher/status
@@ -44,6 +46,9 @@ class LessonMerger {
         b.teachers.firstOrNull?.shortName) {
       return false;
     }
+    // Relevant für Lehrerpläne: gleicher Lehrer/Fach/Raum, aber verschiedene
+    // Klassen dürfen nicht zu einem Block verschmelzen.
+    if (!listEquals(a.classNames, b.classNames)) return false;
     if (a.status != b.status) return false;
     // Lower bound on the gap — without it, two identical-metadata lessons that
     // overlap in time would silently collapse into one.