Retrieve the full details of a single listing by its hashid. Returns the complete ListingResource projection including parcel data, all attribute details, and attachments: photos, plus the public documents the broker attached (brochures, offering memoranda, site plans) with their filename and a direct download URL. Broker contact is included only when the requesting user is authorised to manage the listing; such a user also gets every lease suite with its id and status, the rows update_listing takes back.