show classname instead of teacher name in teacher timetable view

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

@@ -0,0 +1,19 @@
+import '../../../../api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
+
+final RegExp _whitespaceRun = RegExp(r'\s+');
+
+/// Collapses any line-break or whitespace run to a single space and trims.
+/// Returns null when input is null or fully whitespace. Webuntis sometimes
+/// returns multi-line values like "A30\n4" — this normalizes those so labels
+/// render on a single line.
+String? collapseWhitespace(String? s) {
+  if (s == null) return null;
+  final cleaned = s.replaceAll(_whitespaceRun, ' ').trim();
+  return cleaned.isEmpty ? null : cleaned;
+}
+
+/// "7a, 7b" — shared by the calendar tile factory and the home-widget mapper
+/// so both surfaces render identical class labels on teacher plans.
+extension LessonClassLabel on McTimetableEntry {
+  String? get classLabel => collapseWhitespace(classNames.join(', '));
+}