Databases is now just two *geoip2.Reader fields with Open/Close/PrintInfo.
OpenDatabases still auto-discovers conf and downloads stale .mmdb files
via httpcache before opening, but it no longer runs background goroutines
or holds atomic pointers. Long-running callers that want refresh can wire
httpcache.Cacher to atomic.Pointer themselves.
check-ip drops geo.Init/geo.Run — OpenDatabases does the fetch+open work
itself, and a one-shot CLI doesn't need background refresh.