ateapi: the worker record stores a single pod IP, so dual-stack workers lose a family

Sub-task of #246, part of bowei's [step 3](https://github.com/agent-substrate/substrate/issues/246#issuecomment-4771177881).

The worker syncer copies `pod.Status.PodIP` into the worker record's scalar `Ip` field (`cmd/ateapi/internal/controlapi/syncer.go:146`, and the change check at :172). `PodIP` is the primary family only, so on a dual-stack cluster the secondary address is discarded before any consumer sees it and the router can only ever reach a worker over the primary family.

`pod.Status.PodIPs` carries both. The fix touches the stored `Worker` shape rather than just the syncer: the record has to hold an address per family, and each consumer picks one.