A named bookable unit of a service — Room 101, Chair 2, Court A.
When a service has ANY active units, its capacity becomes the count of
active units (overriding seats) and every confirmed/pending booking is
auto-assigned the least-loaded free unit inside the locked create
(PhoenixKitBookings.Bookings). Services without units keep the pooled
seats counter (Checkfront/Planyo-style) — the Booqable trackable
dichotomy, deferred per service.
Summary
Functions
service_uuid is stamped by the context, never cast.