inventory.ip_version (or NETBOX_INVENTORY_IP_VERSION): both (default),
v4 or v6; the ip-addresses source filters by family server-side, the
virtual-machines source picks primary_ip4/primary_ip6 for ansible_host.
config.yaml next to the script (or $NETBOX_INVENTORY_CONFIG) with environment
variable overrides, requests session with token auth, paginated list fetching
and readable error reporting.
