Migrate service control from ZMQ to SSH with real-time progress

Replace ZMQ-based service start/stop commands with SSH execution in tmux
popups. This provides better user feedback with real-time systemctl output
while eliminating blocking operations from the main message processing loop.

Changes:
- Service start/stop now use SSH with progress display
- Added backup functionality with 'B' key
- Preserved transitional icons (↑/↓) for immediate visual feedback
- Removed all ZMQ service control commands and handlers
- Updated configuration to include backup_alias setting
- All operations (rebuild, backup, services) now use consistent SSH interface

This ensures stable heartbeat processing while providing superior user
experience with live command output and service status feedback.

dashboard/src/app.rs

@@ -9,14 +9,13 @@ use std::io;
 use std::time::{Duration, Instant};
 use tracing::{debug, error, info, warn};
 
-use crate::communication::{AgentCommand, ServiceAction, ZmqCommandSender, ZmqConsumer};
+use crate::communication::{ZmqConsumer};
 use crate::config::DashboardConfig;
 use crate::metrics::MetricStore;
 use crate::ui::{TuiApp, UiCommand};
 
 pub struct Dashboard {
     zmq_consumer: ZmqConsumer,
-    zmq_command_sender: ZmqCommandSender,
     metric_store: MetricStore,
     tui_app: Option<TuiApp>,
     terminal: Option<Terminal<CrosstermBackend<io::Stdout>>>,
@@ -58,14 +57,6 @@ impl Dashboard {
             }
         };
 
-        // Initialize ZMQ command sender
-        let zmq_command_sender = match ZmqCommandSender::new(&config.zmq) {
-            Ok(sender) => sender,
-            Err(e) => {
-                error!("Failed to initialize ZMQ command sender: {}", e);
-                return Err(e);
-            }
-        };
 
         // Try to connect to hosts but don't fail if none are available
         match zmq_consumer.connect_to_predefined_hosts(&config.hosts).await {
@@ -124,7 +115,6 @@ impl Dashboard {
 
         Ok(Self {
             zmq_consumer,
-            zmq_command_sender,
             metric_store,
             tui_app,
             terminal,
@@ -290,22 +280,6 @@ impl Dashboard {
     /// Execute a UI command by sending it to the appropriate agent
     async fn execute_ui_command(&self, command: UiCommand) -> Result<()> {
         match command {
-            UiCommand::ServiceStart { hostname, service_name } => {
-                info!("Sending user start command for service {} on {}", service_name, hostname);
-                let agent_command = AgentCommand::ServiceControl {
-                    service_name: service_name.clone(),
-                    action: ServiceAction::UserStart,
-                };
-                self.zmq_command_sender.send_command(&hostname, agent_command).await?;
-            }
-            UiCommand::ServiceStop { hostname, service_name } => {
-                info!("Sending user stop command for service {} on {}", service_name, hostname);
-                let agent_command = AgentCommand::ServiceControl {
-                    service_name: service_name.clone(),
-                    action: ServiceAction::UserStop,
-                };
-                self.zmq_command_sender.send_command(&hostname, agent_command).await?;
-            }
             UiCommand::TriggerBackup { hostname } => {
                 info!("Trigger backup requested for {}", hostname);
                 // TODO: Implement backup trigger command