Set Camera Group Members

Replace the camera group's membership with this exact set.

Replace-set, not per-camera add/remove: the picker submits a set, and rewriting the whole set in one transaction is what makes the change atomic — two concurrent PUTs would otherwise interleave into the UNION of both sets, leaving a camera someone just removed still silenced by this group's schedule while the UI shows it removed.

An empty list empties the camera group. If the group has a schedule, that schedule then governs nobody; the group itself survives.

The camera group's membership as it stands after the request.

The PUT is a REPLACE-SET: this payload is the authoritative new state, not a delta. A camera absent from it is no longer a member, and this group's schedule no longer contributes to that camera's monitoring state.