Fix service start/stop toggle and nixos-rebuild permissions

- Implement proper service status checking for start/stop toggle
- Space key now checks current service status and toggles appropriately
- Active services get stopped, inactive services get started
- Fix nixos-rebuild sudo permissions (remove invalid package reference)
- Use only /run/current-system/sw/bin/nixos-rebuild path

dashboard/src/app.rs

@@ -280,12 +280,22 @@ impl Dashboard {
                 self.zmq_command_sender.send_command(&hostname, agent_command).await?;
             }
             UiCommand::ServiceStartStop { hostname, service_name } => {
-                // For now, we'll implement this as a start command
-                // TODO: Check current service status and toggle appropriately
-                info!("Sending start command for service {} on {}", service_name, hostname);
+                // Check current service status and toggle appropriately
+                let current_status = self.get_service_status(&hostname, &service_name);
+                let action = match current_status {
+                    Some(status) if status.contains("active") || status.contains("running") => {
+                        info!("Sending stop command for active service {} on {}", service_name, hostname);
+                        ServiceAction::Stop
+                    }
+                    _ => {
+                        info!("Sending start command for inactive service {} on {}", service_name, hostname);
+                        ServiceAction::Start
+                    }
+                };
+                
                 let agent_command = AgentCommand::ServiceControl {
                     service_name,
-                    action: ServiceAction::Start,
+                    action,
                 };
                 self.zmq_command_sender.send_command(&hostname, agent_command).await?;
             }
@@ -304,6 +314,22 @@ impl Dashboard {
         }
         Ok(())
     }
+
+    /// Get current service status from metrics to determine start/stop action
+    fn get_service_status(&self, hostname: &str, service_name: &str) -> Option<String> {
+        let metrics = self.metric_store.get_metrics_for_host(hostname);
+        
+        // Look for systemd service status metric
+        for metric in metrics {
+            if metric.name == format!("systemd_{}_status", service_name) {
+                if let cm_dashboard_shared::MetricValue::String(status) = &metric.value {
+                    return Some(status.clone());
+                }
+            }
+        }
+        
+        None
+    }
 }
 
 impl Drop for Dashboard {