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

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

@@ -1,31 +1,39 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:syncfusion_flutter_calendar/calendar.dart';
 
 import '../../../../api/marianumconnect/queries/timetable_get_week/timetable_get_week_response.dart';
 import '../../../../extensions/date_time.dart';
 import '../../../../extensions/text.dart';
 import '../../../../routing/app_routes.dart';
+import '../../../../state/app/modules/timetable/bloc/timetable_bloc.dart';
 import '../../../../state/app/modules/timetable/bloc/timetable_state.dart';
 import '../../../../widget/debug/debug_tile.dart';
 import '../../../../widget/details_bottom_sheet.dart';
 import '../data/lesson_type_label.dart';
+import '../subject_colors/subject_color_picker.dart';
 
 class LessonSheet {
   static void show(
     BuildContext context,
     TimetableState? state,
     Appointment appointment,
-    McTimetableEntry lesson,
-  ) {
+    McTimetableEntry lesson, {
+    bool canEditSubjectColor = false,
+  }) {
     if (state == null) return;
 
+    // In Fremdansichten würde der Farb-Button die eigene, globale Fach-Farbe
+    // ändern, ohne dass sich der fremde Plan aktualisiert — daher nur im
+    // eigenen Plan anbieten. Die Einfärbung (eigene Farben) bleibt.
+    final bloc = context.read<TimetableBloc>();
     final subjectShort = lesson.subjects.firstOrNull;
-    final headerLong = subjectShort == null
+    final subjectEntry = subjectShort == null
         ? null
         : state.subjects?.result
               .where((s) => s.shortName == subjectShort)
-              .firstOrNull
-              ?.longName;
+              .firstOrNull;
+    final headerLong = subjectEntry?.longName;
     // Bei Stunden ohne Fach (Pausenaufsicht etc.) den Lesson-Type-Titel
     // einsetzen — sonst stünde im Header nur ein generisches "?".
     final headerTitle = subjectShort != null
@@ -50,6 +58,18 @@ class LessonSheet {
           headerLongName.isNotEmpty ? '$timeRange\n$headerLongName' : timeRange,
         ),
         isThreeLine: headerLongName.isNotEmpty,
+        trailing: canEditSubjectColor && subjectShort != null
+            ? TimetableColorHeaderButton(
+                initialColorName: subjectEntry?.color,
+                pickerTitle: (headerLong != null && headerLong.isNotEmpty)
+                    ? 'Farbe: $headerLong'
+                    : 'Farbe: $subjectShort',
+                pickerSubtitle: 'Nur reguläre Stunden werden eingefärbt',
+                onSelected: (option) =>
+                    bloc.setSubjectColor(subjectShort, option.name),
+                onReset: () => bloc.clearSubjectColor(subjectShort),
+              )
+            : null,
       ),
       children: (_) => <Widget>[
         ListTile(