SIP Proxy Router - installer
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Turns any OpenWrt router into a locked-down WireGuard local-IP proxy.
1. Router on stock OpenWrt (internet available the first time).
2. Copy install.sh onto the router (scp or LuCI upload).
3. SSH in and run:   sh install.sh
Installs WireGuard, self-enrolls with the voice server, builds the tunnel,
MASQUERADEs the server's SIP traffic out this router's WAN, LOCKS the firewall
(SSH only from the voice server over the tunnel), and serves a local setup page
at  http://<router-LAN-IP>/cgi-bin/setup  for Wi-Fi uplink + Access Point.
The router then shows up under "SIP Proxy Routers" in the admin panel.
