port to Pi 4 'wan': onboard eth0+wlan0 as NM WANs, AP stack verbatim

The USB hub (5GHz + 2.4GHz AP dongles, Starlink + LAN RTL8153s) moves over
from wayback; MAC-derived wlx*/enx* names travel with it, so hostapd/
networkd/cockpit configs are unchanged. Pi diffs only: failover WAN list
(wlan0 wifi 100, eth0 150, starlink USB 200, Koodo 300), cpu_thermal
sensor, bcm2835 watchdog 10s, no HA DNAT/lease, and deploy.sh drops
battery/lid/heartbeat/ZT-dns. Netplan reference in ap/50-van-wan.yaml.

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

failover/config.json

@@ -9,7 +9,8 @@
     "http://cp.cloudflare.com/"
   ],
   "wans": [
-    { "name": "wifi",     "device": "wlp1s0",          "metric": 100 },
+    { "name": "wifi",     "device": "wlan0",           "metric": 100 },
+    { "name": "eth",      "device": "eth0",            "metric": 150 },
     { "name": "starlink", "device": "enxd8ec5eeb3512", "metric": 200 },
     { "name": "cellular", "connection": "Koodo",       "metric": 300 }
   ]