Fin services: stop add-brands-to-service timing out
addPartnerServiceAndBrandService looked up partner_service and partner_service_brand
once per store x brand (each SELECT auto-flushing a growing session), so adding a brand
to a service with many brands (e.g. NOTHING on Bajaj) ran past the request timeout.
Load existing rows in two queries and insert only what's missing. The add endpoints
(fofo + web v2) also skip brands already on the service, so a retry can't duplicate them.