country/country_auto in buildProbeNodeView now come from a local
MMDB lookup of the node's public address (held v4, held v6, seen
v4, seen v6) instead of the pin alone / a hardcoded empty string.
Layered data: local file in the data folder wins, embedded factory
snapshot is the fallback, no database means the pre-flag empty
shape. A weekly job conditionally downloads a fresher copy,
validates it, atomically replaces the local file and hot-swaps the
reader; no URL configured (geoipCountryDefaultURL / the
geoip_country_url setting) means the updater stays silent. No
address ever leaves the master.
