Ask Multigest to configure a point of sale for ad export.

Body: {"pv_id": int, "brand_ids": [int, ...]}

brand_ids is plural because several brands of the same company can be blocked on the SAME point of sale; the tab groups them into one banner and this endpoint into ONE ticket, rather than N near-identical ones.

Returns 200 {"ticket_id", "status", "pv_id", "pv_name", "brand_ids"}.

Refusals (the ticket IS the product here — never a silent success): 400 invalid input / no identifiable user / open-ticket ceiling 403 brand or PV does not belong to the caller's company 409 brand not provisioned at all, or location already configured, or a request is already open (carries ticket_id) 429 duplicate press debounced