Remove ZMQ debug packet counter from display

- Remove ZMQ stats display from system widget
- Remove update_zmq_stats method
- Remove zmq_packets_received and zmq_last_packet_age fields
- Clean up display to only show essential information

dashboard/src/ui/mod.rs

@@ -110,14 +110,6 @@ impl TuiApp {
                 host_widgets.system_widget.update_from_agent_data(agent_data);
                 host_widgets.services_widget.update_from_agent_data(agent_data);
 
-                // Update ZMQ stats
-                if let Some(zmq_stats) = metric_store.get_zmq_stats(&hostname) {
-                    host_widgets.system_widget.update_zmq_stats(
-                        zmq_stats.packets_received,
-                        zmq_stats.last_packet_age_secs
-                    );
-                }
-
                 host_widgets.last_update = Some(Instant::now());
             }
         }