Release Ticket Lock

Ends the lock on this ticket right now.

?mine=true (a page LEAVING the ticket) deletes only the caller's own row, so a closing tab can never delete a colleague's or the new owner's lock (issue #4169, 2026-10-07). Without it the release is unqualified by holder -- Take over, and the "an ordinary person on the desk can un-stick this" escape hatch docs/SUPERVISION_DESK.md requires for a lock that looks abandoned but has not expired yet. A no-op, not a 404, when nothing matched (service.release_ticket_lock's own docstring).