Queue page offsets for this file's current version, if it can have them (PIT-9030).

Called by the Action Manager ensure-pdf-pages handler on File Published.
202 {"queued": true} when queued; otherwise 200 {"queued": false, "reason": ...}
(a permanent property of the row, a remembered terminal outcome of this version,
or already_queued). Idempotent per (file, version) for an hour, so duplicate
events and the handler's retries enqueue once.