Template remaining host-specific values (WAN wifi, LAN/eth0, NVMe, nftables)

nftables.conf hardcoded the R5C network, van-br0-setup.service the R5C
interfaces and several configs wlan0/eth0. All now come from the host
config; the onboard LAN port is skipped when ONBOARD_LAN_IFACE is empty.

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

ap/van-br0-setup.service

@@ -5,8 +5,8 @@ Wants=systemd-networkd.service hostapd.service
 
 [Service]
 Type=oneshot
-ExecStart=/bin/bash -c "brctl addif br0 enP2p33s0 2>/dev/null || true"
-ExecStart=/bin/bash -c "brctl addif br0 wlp1s0 2>/dev/null || true"
+ExecStart=/bin/bash -c "brctl addif br0 @LAN_IFACE@ 2>/dev/null || true"
+ExecStart=/bin/bash -c "brctl addif br0 @WIFI_5G_IFACE@ 2>/dev/null || true"
 RemainAfterExit=yes
 
 [Install]