feat: improve MQTT reconnection handling + document arrival notifier

- Add keepalive (60s), reconnectPeriod (5s), connectTimeout (30s)
- Add offline/close event handlers with proper logging
- Document Tesla Arrival Notifier setup in README
- Document systemd service installation

arrival-notifier.js

@@ -188,12 +188,17 @@ async function main() {
     username: config.mqtt.username,
     password: config.mqtt.password,
     rejectUnauthorized: true,
+    keepalive: 60,           // Send ping every 60s
+    reconnectPeriod: 5000,   // Retry every 5s on disconnect
+    connectTimeout: 30000,   // 30s connection timeout
   };
 
   const client = mqtt.connect(config.mqtt.url, mqttOptions);
   const prefix = `teslamate/cars/${config.carId}`;
+  let isConnected = false;
 
   client.on('connect', () => {
+    isConnected = true;
     log.info('Connected to MQTT');
     
     // Subscribe to relevant topics
@@ -235,7 +240,22 @@ async function main() {
   });
 
   client.on('error', (err) => log.error('MQTT error:', err.message));
-  client.on('reconnect', () => log.info('Reconnecting...'));
+  
+  client.on('reconnect', () => {
+    log.info('Reconnecting to MQTT...');
+  });
+
+  client.on('close', () => {
+    if (isConnected) {
+      log.info('MQTT connection closed');
+      isConnected = false;
+    }
+  });
+
+  client.on('offline', () => {
+    log.info('MQTT client offline');
+    isConnected = false;
+  });
 
   // Graceful shutdown
   process.on('SIGINT', () => {