Bug: ${UI} token in subflow ui-template ui field gets rewritten to a hardcoded ID

### Current Behavior

**Setup:** Subflow with a conf-types env var UI (type ui-base). Three ui-template nodes inside the subflow with "ui": "${UI}", per our docs. Packaged as an npm module via the FlowFuse Library.

### Steps To Reproduce

After deploy + refresh, the ui field is rewritten from ${UI} to a literal hex ID. On instances whose ui-base doesn't match that ID, the widget silently fails to render. No error, no node status, no log.

### Environment

- Dashboard version: 1.30.2
- Node-RED version: 4.1.10
- Platform/OS: Mac OSX
- Browser: Chrome

What's rewriting ${UI} to a literal ID on deploy?
Can we surface a warning when a subflow ui-template's ui reference is unresolvable, so this fails loud instead of silent?