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>

cockpit/vanrouter/vanrouter.js

@@ -15,7 +15,7 @@ const APS = [
 ];
 const PREFER_FILE = "/run/van-failover/prefer";  // van-failover reads this to pick the preferred WAN
 // Wired LAN bridge ports: clients behind them are found via the bridge FDB.
-const LAN_PORTS = { "eth0": "LAN (eth0)", "@LAN_USB_IFACE@": "LAN (USB)" };
+const LAN_PORTS = { "eth0": "LAN (eth0)", "@LAN_IFACE@": "LAN (USB)" };
 // Starlink dish: gRPC status API on the fixed management IP (reached via the /32
 // link route the netplan profile installs on the RTL8153 uplink).
 const STARLINK = { iface: "@STARLINK_IFACE@", dish: "192.168.100.1:9200" };