[Bookings] Refactor Bookings Page

[parth-io]

• [ ] Cache calculations (such as isDisabled for all 6 venues) with useMemo
• [ ] Cleanup and refactor bookings.tsx and BookingVenueCol
• [ ] making booking more than 4 timeslots unselectable unless admin
• [ ] For CalendarCell that has a modal if there are too many bookings to display, the modal appears on the centre of the screen. We can centre the modal to the CalendarCell and reduce its size instead, for a cleaner look
• [ ] Split bookings components into separate files

[zsh-eng]

TODO: Seed the database with many bookings to test the benefit of useMemo Steps:

1. Change the DATABASE_URL in the backend .env file to the relevant DB that matches the frontend's
2. Edit the function generateBookingData in the seed file
3. Run npm run prisma:reset