migrated custom timetable events to Marianum-Connect and refactored push notification handling

lib/view/pages/timetable/custom_events/custom_event_edit_dialog.dart

@@ -57,6 +57,10 @@ class _CustomEventEditDialogState extends State<CustomEventEditDialog> {
     text: widget.existingEvent?.description ?? widget.initialDescription,
   );
   late String _rrule = widget.existingEvent?.rrule ?? '';
+  // Für neue Termine standardmäßig an, bestehende behalten ihren Wert. Migrierte
+  // mhsl-Termine tragen ausgeschaltet (Modell-Default), da sie nie ein Serien-
+  // Ferien-Flag hatten.
+  late bool _skipHolidays = widget.existingEvent?.skipHolidays ?? true;
   late CustomTimetableColors _color = CustomTimetableColors.values.firstWhere(
     (e) => e.name == widget.existingEvent?.color,
     orElse: () => TimetableColors.defaultColor,
@@ -150,6 +154,7 @@ class _CustomEventEditDialogState extends State<CustomEventEditDialog> {
       endDate: endDate,
       color: _color.name,
       rrule: _rrule,
+      skipHolidays: _rrule.trim().isEmpty ? false : _skipHolidays,
       createdAt: DateTime.now(),
       updatedAt: DateTime.now(),
     );
@@ -297,6 +302,18 @@ class _CustomEventEditDialogState extends State<CustomEventEditDialog> {
               },
             ),
           ),
+          if (_rrule.trim().isNotEmpty) ...[
+            const Divider(),
+            SwitchListTile(
+              secondary: const Icon(Icons.beach_access_outlined),
+              title: const Text('In den Ferien ausblenden'),
+              subtitle: const Text(
+                'An Ferientagen wird der Termin nicht angezeigt',
+              ),
+              value: _skipHolidays,
+              onChanged: (v) => setState(() => _skipHolidays = v),
+            ),
+          ],
         ],
       ),
     ),