Adds an opt-in environment variable to suppress the npm-registry update
check. When set, three things change:
1. checkLatestVersion() returns immediately (no outbound fetch)
2. startVersionCheck() does not arm the 30-minute interval
3. /api/health returns webui_latest='' and webui_update_available=false
Use case: hermes-web-ui is bundled inside a packaged distribution like
a desktop app where the user cannot `npm install -g hermes-web-ui@latest`
to apply an upgrade. The 'update available' prompt is then misleading
(the user would have to wait for the wrapper app to ship a new release),
and the recurring HTTPS call to the npm registry is unnecessary noise.
Set HERMES_WEB_UI_DISABLE_UPDATE_CHECK=true | 1 | on | yes to disable.
The default behavior is unchanged.
Discussed in #1091 — proposed by @EKKOLearnAI.
