WAN and VPN requests are served by local port 1053 and `wan.uninsane.org`.
LAN requests are served by port 53 and `servo.lan.uninsane.org`.
i'm not *super* fond of this. a recursive resolver of uninsane.org via the VPN will only ever get WAN addresses (broken).
we may prefer to do IP-based responses, maybe via the same Linux firewall rules that forward from VPN namespace to root namespace
although the systemd wantedBy directive is working,
`before` seems to be ignored when the unit fails. so on first run,
dyn-dns runs, fails (poor net connectivity), then trust-dns starts
(fails), then they both restart 10s later.
it's not great, but good enough. also, wan IP is persisted, so this
likely won't happen much in practice.
