Make router IP address configurable via deploy.conf

Add GATEWAY_IP, GATEWAY_PREFIX, GATEWAY_NETWORK, DHCP_RANGE_START, and
DHCP_RANGE_END variables to deploy.conf. Update ap/21-van-br0.network,
ap/van-ap-dnsmasq.conf, and ap/nftables.conf to use @TOKEN@ placeholders
for IP configuration instead of hardcoding 10.42.x addresses.

This allows deploying the same configuration to multiple routers on
different networks (e.g., Pi 5 on 10.42.0.x and R5C on 10.42.1.x) by
simply editing deploy.conf before running ./deploy.sh.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

deploy.sh

@@ -23,6 +23,11 @@ render() {  # render <file> -> stdout, with @TOKEN@ placeholders substituted
         -e "s|@STARLINK_IFACE@|$STARLINK_IFACE|g" \
         -e "s|@MODEM_USB_VENDOR@|$MODEM_USB_VENDOR|g" \
         -e "s|@DNS_RESOLVERS@|$DNS_RESOLVERS|g" \
+        -e "s|@GATEWAY_IP@|$GATEWAY_IP|g" \
+        -e "s|@GATEWAY_PREFIX@|$GATEWAY_PREFIX|g" \
+        -e "s|@GATEWAY_NETWORK@|$GATEWAY_NETWORK|g" \
+        -e "s|@DHCP_RANGE_START@|$DHCP_RANGE_START|g" \
+        -e "s|@DHCP_RANGE_END@|$DHCP_RANGE_END|g" \
         "$1"
 }
 install_rendered() {  # install_rendered <src> <dst> [mode]
@@ -160,18 +165,21 @@ install -D -m0644 modem/van-sms-watch.service /etc/systemd/system/van-sms-watch.
 # are PolicyKit-gated). Not a service, just a tool: sudo van-sms-send <number> <text>
 install -D -m0755 modem/van-sms-send /usr/local/sbin/van-sms-send
 
-echo "== cockpit plugin =="
-install -d /usr/share/cockpit/vanrouter
-for f in cockpit/vanrouter/*; do
-    b=$(basename "$f")
-    if [ "$b" = "vanrouter.js" ]; then
-        install_rendered "$f" "/usr/share/cockpit/vanrouter/$b"
-    else
-        install -m0644 "$f" "/usr/share/cockpit/vanrouter/$b"
-    fi
-done
-# Bridge fd headroom (Python bridge frees spawn pipes only at GC; 1024 is too tight)
-install -D -m0644 cockpit/cockpit-session-nofile.conf /etc/systemd/system/cockpit-session@.service.d/nofile.conf
+if [ "$SKIP_COCKPIT" -ne "1" ]; then
+    echo "== cockpit plugin =="
+    install -d /usr/share/cockpit/vanrouter
+    for f in cockpit/vanrouter/*; do
+        b=$(basename "$f")
+        if [ "$b" = "vanrouter.js" ]; then
+            install_rendered "$f" "/usr/share/cockpit/vanrouter/$b"
+        else
+            install -m0644 "$f" "/usr/share/cockpit/vanrouter/$b"
+        fi
+    done
+    # Bridge fd headroom (Python bridge frees spawn pipes only at GC; 1024 is too tight)
+    install -D -m0644 cockpit/cockpit-session-nofile.conf /etc/systemd/system/cockpit-session@.service.d/nofile.conf
+fi    
+
 # The Starlink card queries the dish's gRPC API; grpcurl isn't packaged in apt.
 command -v grpcurl >/dev/null 2>&1 \
     || warn "grpcurl missing (Starlink card will say so): install linux_arm64 binary from github.com/fullstorydev/grpcurl/releases"