Commit a staged upload to a dataset
Requires onboarding_admin + CSRF. Re-parses the previously staged upload, normalizes rows against the caller-supplied column mapping, and writes a new versioned datasets/records snapshot (records de-duplicated by content hash). Auto-detected PII columns are persisted as pii_field_policies. Enqueues a materialize_insights platform job (idempotency key materialize:{tenant_id}:{dataset_id}:{version}) and writes a control.audit_log row (dataset_ingested). Calling this again for an already-committed upload returns the existing dataset instead of re-processing it. 404 for an unknown upload id, 409 if the upload previously failed validation, 503 if object storage is unavailable.