update data purging, re-enable channel selection

src/mqtt/client.js

@@ -344,10 +344,11 @@ class MeshtasticMQTTClient {
   }
 
   // Send a text message
-  async sendTextMessage(from, text) {
+  async sendTextMessage(from, text, channel=0) {
     try {
       const message = JSON.stringify({
         from: from,
+        channel: channel,
         type: 'sendtext',
         payload: text
       });