feat(openwrt): WAN/WISP setup from the UI with WiFi network scan

New RPC methods:
- openwrt.scan-wifi: triggers iwinfo scan on the router radio,
  returns networks sorted by signal strength
- openwrt.configure-wan: creates UCI wireless.wwan (sta mode) +
  network.wwan (DHCP) + adds wwan to firewall WAN zone, then
  calls `wifi reload`

get-status now includes a `wan` object with configured/ssid/ip/
internet fields so the UI can show current uplink state.

Frontend WAN panel: scan → pick SSID (signal bars) → enter password
→ apply. Shows "Configure WAN first" hint above TollGate install
button when internet is not available.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/archipelago/src/api/rpc/middleware.rs

@@ -71,6 +71,9 @@ pub(super) fn sanitize_error_message(msg: &str) -> String {
         "No pre-built TollGate",
         "opkg not found",
         "apk update failed",
+        "No wireless interface",
+        "No wireless radio",
+        "Missing required field",
     ];
     for prefix in &user_facing_prefixes {
         if msg.starts_with(prefix) {