Delete Usage Rows

Delete imported usage rows by explicit ids or by filter (standalone).

Target either the current selection (ids) or everything matching a filter (by_filter: true plus optional source / model / user_id / status / date range / priced). Only imported rows (counts_toward_budget = false) are ever removed: enforced gateway rows and the spend ledger (users.spend) are untouched, so a delete can never desync a budget. Master-key only.