Deferred Credit Pack Activation - Start on First Use

Currently, credit packs are activated and their expiration countdown begins immediately upon purchase. This creates friction for customers who buy packs in advance (e.g., during promotions or when planning their schedule) but do not make their first booking until much later.

The solution could be adding the option to configure credit pack expiry based on the date of the member's first booking made using that specific pack, rather than the purchase date.