Limit timetable scrolling so no errors occur

lib/view/pages/timetable/timetable.dart

@@ -72,6 +72,12 @@ class _TimetableState extends State<Timetable> {
             return PlaceholderView(
               icon: Icons.calendar_month,
               text: "Webuntis error: ${value.error.toString()}",
+              button: TextButton(
+                child: const Text("Neu laden"),
+                onPressed: () {
+                  Provider.of<TimetableProps>(context, listen: false).resetWeek();
+                },
+              ),
             );
           }
 
@@ -90,6 +96,9 @@ class _TimetableState extends State<Timetable> {
               view: CalendarView.workWeek,
               dataSource: _buildTableEvents(value),
 
+              maxDate: DateTime.now().add(const Duration(days: 7)),
+              minDate: DateTime.now().subtract(const Duration (days: 14)),
+
               controller: controller,
 
               onViewChanged: (ViewChangedDetails details) {