Delete a config outright — scheduled, current, or past.

Deleting a period that has already started rewrites revenue history (the Revenue tab attributes billing events from these rows), so it is meant for rows that should never have existed: a prospect who backed out before signing, or a mis-entered period. To stop billing a real customer while keeping their history, PATCH effective_until instead of deleting.

By default the adjacent earlier period ending exactly at this config's effective_from is reopened (effective_until back to NULL), undoing the auto-close from creation — unless reopening would overlap another period.