CUB-231: Mosquitto MQTT broker setup on Pi Zero 2 W hub

- Install script for Mosquitto MQTT broker on Pi Zero 2 W (10.60.1.101)
- Persistence enabled with data stored in /var/lib/mosquitto/data/
- Topic ACL configuration for hub, sensor, mobile, and admin users
- systemd service with security hardening (NoNewPrivileges, ProtectSystem)
- Configuration files: mosquitto.conf, acl.conf
- Validation script to verify setup before deployment

mosquitto.service

@@ -0,0 +1,26 @@
+[Unit]
+Description=Mosquitto MQTT Broker
+Documentation=man:mosquitto(8)
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=/usr/sbin/mosquitto -c /etc/mosquitto/conf.d/mosquitto.conf
+ExecReload=/bin/kill -HUP $MAINPID
+Restart=on-failure
+RestartSec=5
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=mosquitto
+
+# Resource limits
+LimitNOFILE=65535
+
+# Security hardening
+NoNewPrivileges=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/var/log/mosquitto /var/lib/mosquitto /etc/mosquitto
+
+[Install]
+WantedBy=multi-user.target