Mirror the Admin UI Server-Timing opt-in for user-facing pages so
authenticated callers can inspect total/app/db/redis/deps metrics on
session, profile, keys, usage, payment, and related user APIs.
- Collect when X-User-UI-Request=1 or path is on the user allowlist
- Emit for non-admin only on allowlisted paths (header is not auth)
- Exclude payment public/webhook surfaces
- Mark matching SPA requests and allow the new CORS request header
bestony