feat(admin-ui): add configurable Admin UI domain routing

changelog.md

@@ -2,6 +2,20 @@
 
 ## Pending
 
+### Features
+
+- add configurable Onebox Admin UI domain
+  - expose Admin UI domain in settings
+  - sync the Admin UI route as a first-class dcrouter gateway route
+  - keep Admin UI routing separate from app service routes
+- add configurable Admin UI domain routing (admin-ui)
+  - Expose and validate the Admin UI domain in settings
+  - Sync the Admin UI as a dedicated dcrouter gateway route and SmartProxy route
+  - Preserve configured and legacy Admin UI routes during stale-route reconciliation
+
+### Fixes
+
+- preserve Onebox Admin UI routes during external gateway stale-route reconciliation
 
 ## 2026-05-24 - 1.29.0