implemented custom subject colors for the timetable and unified the color palette system

lib/state/app/modules/timetable/bloc/timetable_bloc.dart

@@ -121,6 +121,27 @@ class TimetableBloc
     await _refreshCustomEvents();
   }
 
+  /// Setzt die persönliche Farbe eines Fachs (Schlüssel: Fach-Kürzel) und lädt
+  /// die Fächer neu, damit die eingebettete Farbe im Kalender wirkt.
+  Future<void> setSubjectColor(String subjectShort, String color) async {
+    await repo.data.setSubjectColor(subjectShort, color);
+    await _refreshSubjects();
+  }
+
+  Future<void> clearSubjectColor(String subjectShort) async {
+    await repo.data.removeSubjectColor(subjectShort);
+    await _refreshSubjects();
+  }
+
+  Future<void> _refreshSubjects() async {
+    final subjects = await repo.data.getSubjects(renew: true);
+    add(
+      DataGathered(
+        (s) => s.copyWith(subjects: subjects, dataVersion: s.dataVersion + 1),
+      ),
+    );
+  }
+
   Future<void> _loadCurrentWeek(
     DateTime startDate,
     DateTime endDate, {