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

lib/view/pages/timetable/details/appointment_details_dispatcher.dart

@@ -10,13 +10,20 @@ class AppointmentDetailsDispatcher {
   static void show(
     BuildContext context,
     TimetableState? state,
-    Appointment appointment,
-  ) {
+    Appointment appointment, {
+    bool canEditSubjectColor = false,
+  }) {
     final id = appointment.id;
     if (id is! ArbitraryAppointment) return;
 
     id.when(
-      lesson: (entry) => LessonSheet.show(context, state, appointment, entry),
+      lesson: (entry) => LessonSheet.show(
+        context,
+        state,
+        appointment,
+        entry,
+        canEditSubjectColor: canEditSubjectColor,
+      ),
       custom: (event) => CustomEventSheet.show(context, event),
     );
   }