The /api/custom-domains endpoint changed shape with the slot-pool split
in commit f2b81ee — it now returns { items, counts, limits } where it
used to return a bare CustomDomain[]. The hook was still matching
Array.isArray(res) or res.domains and silently fell back to an empty
list, so a successful POST went unreflected on the blocker page (user
reported "kein fehler aber domain taucht nicht in der liste" after
adding communications@only4subscribers.com).
Now reads items / counts / limits when present, prefers the API-driven
counts and limits over the client-side derivation (still kept as a
fallback for the stale-bundle window between deploys). Legacy bare-
array + { domains } shapes still resolve too in case a cached client
hits this code path before the new backend lands.
c2323c1aba