- Created frontend/app/utils/date.ts with formatDate, formatTime, formatDateTime, formatDisplayDate
- Created frontend/e2e/helpers/date.ts with formatDateLocal, getTomorrowDateStr
- Updated all frontend pages and e2e tests to use shared utilities
- Removed duplicate date formatting code from 6 files
Add check to both user and admin cancel endpoints to reject
cancellation of appointments whose slot_start is in the past.
This matches the spec requirement that cancellations can only
happen 'before the appointment'.
Added tests for both user and admin cancel endpoints.
Also includes frontend styling updates.