show classname instead of teacher name in teacher timetable view

android/app/src/main/kotlin/eu/mhsl/marianum/mobile/client/widgets/WidgetData.kt

@@ -33,6 +33,8 @@ data class WidgetLesson(
     val subjectShort: String,
     val subjectLong: String?,
     val room: String?,
+    // On teacher accounts this carries the class label ("7a") instead of the
+    // teacher short name (originalTeacher is null then) — mapped in Dart.
     val teacher: String?,
     val originalTeacher: String?,
     val status: WidgetLessonStatus,