ConfigRevision responses omit scheduledPublishAt/lock fields that are persisted (spec/back-end)

**Behavior:** `config-revisions schedule-publish` returns 200 and the schedule persists (mongo-verified `scheduledPublishAt`, `scheduledPublishLockEdits`, `scheduledPublishLockOthers` on the revision doc), but the ConfigRevision API response omits all three fields — before and after scheduling. FeatureRevision responses include them. CLI behavior is correct; users just can't see or verify a schedule via the API/CLI.

**Fix location:** back-end ConfigRevision response serializer/spec (growthbook repo). No CLI patch/overlay carried.

Start with the back-end ConfigRevision response serializer/spec and compare it with the FeatureRevision response, which already includes the scheduled-publish fields. Exercise config-revisions schedule-publish and verify that scheduledPublishAt, scheduledPublishLockEdits, and scheduledPublishLockOthers appear in the API response before and after scheduling.

Written by the indexing model from the issue text.