docs(flutter,android): keep the push subscription open in README samples

templates/android/README.md.twig

@@ -65,10 +65,10 @@ val push = Push(client, context)
 val subscription = push.subscribe { message ->
     Log.d("Appwrite", "${message.topic}: ${message.data}")
 }
-
-subscription.unsubscribe()
 ```
 
+Keep `subscription` while you want messages, and call `subscription.unsubscribe()` when you stop listening, for example in your activity's `onDestroy()`.
+
 ### Background delivery
 
 A subscription with `background = true` keeps delivering after the app is backgrounded, its process is killed, or the device restarts, until it is unsubscribed or `push.close()` is called (do this on sign-out). No service is kept running: a scheduled job and alarm wake the app every 15 to 60 seconds to reconnect, and the broker replays what was sent in between (`retry = true`). It reconnects with the credential saved at subscribe time, so use a session (`client.setSession(...)`), not a short-lived JWT.

templates/flutter/README.md.twig

@@ -67,10 +67,10 @@ final push = Push(client);
 final subscription = await push.subscribe('news', (message) {
   print('${message.topic}: ${message.data}');
 });
-
-subscription.unsubscribe();
 ```
 
+Keep `subscription` while you want messages, and call `subscription.unsubscribe()` when you stop listening, for example in your widget's `dispose()`.
+
 ### Background delivery on Android
 
 A subscription with `background: true` keeps delivering after the app is backgrounded, killed or the device restarts, until it is unsubscribed or `push.close()` is called (do this on sign-out). The plugin saves the subscription, and a scheduled job and alarm wake the app every 15 to 60 seconds to reconnect; the broker replays what was sent in between (`retry: true`). While the app is not on screen, each message is posted as a notification that opens the app. It reconnects with the credential saved at subscribe time, so use a session rather than a short-lived JWT.