Ech0 authenticated user-list exposed data via public `/api/allusers` endpoint

Ech0 is an open-source, self-hosted publishing platform for personal idea sharing. Prior to version 4.2.0, `GET /api/allusers` is mounted as a public endpoint and returns user records without authentication. This allows remote unauthenticated user enumeration and exposure of user profile metadata. A fix is available in v4.2.0.