Add backend for bookable office hours

[dkwncho]

Summary:

• Created new Booking model, serializer, permission, urls, and viewset
• Moved the schedules package into our codebase as ohq_schedules
• Bookings can only be created with start times of 5-minute intervals (e.g., :00, :05, :10, :15, etc), would need to reflect this on the frontend

Before merging these changes to main:

• How to properly credit the original package creator

To-do after merging these changes to main:

• Confirm new tables (under the name ohq_schedules) were correctly made with the migrated data from the schedules table
• Remove the django-scheduler app from installed apps, base.py, pipfile/uv
• Remove the data migration file (backend/ohq/migrations/0023_migrate_schedule_data.py)