Summary

• Hide the schedule indicator marker when its calendar day is selected.
• Reuse the same marker rule in the calendar screen and home month calendar.
• Add focused unit coverage for selected, unselected, and empty event marker behavior.

Root cause

TableCalendar still rendered its event marker on selected day cells, so the schedule dot overlapped the blue selected-date highlight and made the calendar UI look broken.

Fixes #432

Validation

• flutter analyze
• flutter test test/presentation/shared/components/calendar/schedule_marker_builder_test.dart test/presentation/calendar/screens/calendar_screen_test.dart