Ingest an item + assets through the single governed chokepoint (editor/admin).

Deterministic collection resolution. Precedence: id > auto > none (uncollected).

For auto, the (source_type, source_id) pair is the find-or-create KEY — the caller controls grouping: e.g. uploads use a single project-level key ("upload","uploads") so they share one "Uploads" collection, while an order delivery uses ("order", order_id) so each order gets its own collection. A drone flight / soil survey would use ("flight", flight_id) / ("survey", survey_id).

Where an item came from — sets the item's source FK + the provenance edge.