Refine timezone="auto" so it ALWAYS resolves (drop the "host" sentinel):
- ""/"auto" resolve from the proxy egress when a proxy is set, else from the
host own public IP (direct lookup); an explicit zone is the only opt-out.
- on failure: with a proxy raise; without a proxy fall back to the host TZ.
GeoIP DB now auto-updates against daijro/geoip-all-in-one weekly rebuild:
cache the latest, re-check after GEOIP_REFRESH_DAYS (7), prune old tags,
reuse a stale cache offline; GEOIP_MMDB_VERSION is only the cold fallback.
tests: test_geo.py (37) + test_geoip_update.py; full unit suite 429 green
plus 8 live combinations (proxy / no-proxy / explicit / failing / freshness).
