Template hostapd interface/SSIDs/5GHz radio lines; guard against other-host hardcodes

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KqhjP7nud5gdBg25zCiRk9

ap/hostapd-2g.conf

@@ -1,4 +1,4 @@
-interface=wlx3c3332002066
+interface=@WIFI_2G_IFACE@
 # Second, independent hostapd instance (hostapd-2g.service) — 2.4GHz band of the same
 # VanLink network, bridged into the same br0 segment as the 5GHz AP and the wired port.
 # Separate process on purpose: a USB wedge on one radio must never take down the other.
@@ -8,7 +8,7 @@ ctrl_interface=/var/run/hostapd
 driver=nl80211
 # Same SSID + PSK as 5GHz: dual-band clients pick a band themselves, 2.4-only IoT
 # devices just join. Rename here (e.g. VanLink-2G) if band pinning is ever needed.
-ssid=VanLink2-2G
+ssid=@AP_SSID_2G@
 country_code=CA
 ieee80211d=1
 hw_mode=g