Delete a credentialing workflow and its associated data

Deletes the credentialing workflow identified by id along with its cascaded child records. The delete is not idempotent — a second call for the same id returns 404. The workflow must belong to the caller's tenant; attempting to delete a workflow from another tenant returns 403. Returns 404 if the workflow is not found. Whether the underlying row is hard- or soft-deleted is determined by the DAL and is not asserted here.