Vendor GeoLite2-Country.mmdb in the repository so agent builds still
work when the remote download is unavailable. Update the fetch script
and agent Dockerfile to prefer a fresh download and fall back to the
committed database file.
Agent embeds GeoLite2-Country.mmdb but the file is not checked into the
repository. Download it in CI, Docker, and Makefile build paths via
scripts/fetch-agent-geoip-mmdb.sh, and correct the gitignore exception
path for the geoipdata package.