deploy: host config from /etc/vanlink.conf (hosts/<hostname>.conf)

deploy.conf is replaced by one versioned file per host plus an example.
deploy.sh validates the config, renders every template with a generic
token loop, refuses to install output with leftover @TOKENs and gains
--check/--templates. LAN_USB_IFACE is renamed LAN_IFACE.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ap/22-van-lan.network

@@ -2,7 +2,7 @@
 # gets DHCP/DNS from the same dnsmasq as Wi-Fi clients. NM must leave this device
 # alone (see van-ap-unmanaged.conf) for networkd to own it here.
 [Match]
-Name=@LAN_USB_IFACE@
+Name=@LAN_IFACE@
 
 [Link]
 RequiredForOnline=no