Background probe fetches ipinfo through each pool itself (provider-agnostic
transport), fills an egress IP/country cache (TTL 1h, 8-IP history) and flags
flapping relays as unstable. Periodic state sweeper (10 min) prunes expired
fitness marks, stale geo/ip-history and Freebuff session/cooldown state;
schedulers skip non-server runtimes. Unit tests for the geo cache.