Refactor codebase resolving warnings and remove self-package imports

lib/view/pages/timetable/timetableEvents.dart

@@ -0,0 +1,8 @@
+
+import 'package:syncfusion_flutter_calendar/calendar.dart';
+
+class TimetableEvents extends CalendarDataSource {
+  TimetableEvents(List<Appointment> source) {
+    appointments = source;
+  }
+}