List Admin Top Sources

Each active, published region's latest aggregates — uncached.

The source-logo manager derives the set of top source domains from this so an admin can add a mark the moment a new region is published. Reading the PUBLIC index instead inherited its CDN cache, so a freshly approved region's top source stayed invisible in the manager for the cache window. This admin route sets no cache headers, so it always reflects committed DB state — mirroring why list_admin_regions exists.