Every write path now sets offer_id = catalog_items.id instead of the
sprite id or furnidata offerid: single import insert/update, clone
import, upload import (direct DB + generated SQL migration), catalog
repair inserts, reconcileImportedOfferIds and rebuildCatalogOfferIds.
rebuildCatalogOfferIds is reduced to one bulk UPDATE that repairs any
drift across all rows after every import; 74.838 legacy rows were
repaired on the live database with this change.