Returns a batch of eligible Smart Link offers for the authenticated publisher.

Each item is a reserved visit with its own id and smart_link. Cache the batch briefly
on your server using cache_ttl_seconds (do not re-request on every UI render).

When an end user starts an offer, open smart_link in their browser only. That URL
is a Highpay redirect for humans, not a publisher API call.

HTTP 200 with success=true and an empty ads array means no fill right now.