Keep back-to-back appointments in the same facility when “No Preference” is chosen

When a member books consecutive appointments and picks No Preference (Maximum Availability), each booking is given a facility at random from those free at that time. The member can end up in a different bay for each back-to-back slot, so they have to move halfway through their session.

Request: When no facility is chosen, the system should first try the facility the same member already has booked for the slot directly before or after. It should fall back to the current random choice only if that facility isn’t free.