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>

router-status/config.json

@@ -9,7 +9,7 @@
   "poll_interval_s": 5,
   "wifi_5g_iface": "@WIFI_5G_IFACE@",
   "wifi_2g_iface": "@WIFI_2G_IFACE@",
-  "lan_usb_iface": "@LAN_USB_IFACE@",
+  "lan_usb_iface": "@LAN_IFACE@",
   "starlink_iface": "@STARLINK_IFACE@",
   "starlink_dish": "192.168.100.1:9200",
   "modem_usb_vendor": "@MODEM_USB_VENDOR@",