Add app-managed startup health and UI

[pavelhov]

Summary

• Explain the user-visible or maintainer-facing change.

Verification

• List the commands or checks you ran.
• If this PR changes the GUI, include a screenshot of the UI change in the description.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.