Add @ReleasedBy parameter to sp_ReleaseExternalIdReservation via a new EF
migration so the operator principal (not the shared SQL account) is recorded
in ExternalIdReservation.ReleasedBy and ConfigAuditLog.Principal.
ReservationService.ReleaseAsync gains a releasedBy parameter; Reservations.razor
resolves the signed-in user from AuthenticationState and passes it through.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>