Fix watchdog timeout and MQTT connectivity issues

Problem: R5C spontaneously rebooted due to hardware watchdog timeout
Cause 1: van-gps-owntracks in infinite restart loop (MQTT connect failed)
Cause 2: mosquitto only listening on localhost, so clients couldn't connect
Solution:
- Add restart limits to van-gps-owntracks and van-li3-battery services
  (max 3 restarts per 5 minutes prevents infinite restart loops)
- Configure mosquitto to listen on all interfaces (0.0.0.0:1883)
- Deploy mosquitto listener config via deploy.sh
- Restart mosquitto during deploy to apply config changes

This prevents the system from hitting the 11-second hardware watchdog timeout
when services crash and systemd auto-restarts them indefinitely.

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

ap/nftables.conf.bak

@@ -0,0 +1,11 @@
+#!/usr/sbin/nft -f
+# van-router NAT — masquerade LAN out whatever the WAN of the moment is
+# (anything that is NOT the LAN bridge br0: ethernet/Starlink, wifi, future 4G)
+table ip van_router_nat
+delete table ip van_router_nat
+table ip van_router_nat {
+    chain postrouting {
+        type nat hook postrouting priority srcnat; policy accept;
+        ip saddr 10.42.0.0/24 oifname != "br0" masquerade
+    }
+}