feat: add periodic tray menu refresh and normalize tunnel metrics field names

Add background task to refresh tray menu every 5 seconds to keep status display current. Add RawTunnelMetrics type and normalizeTunnelMetrics helper to handle both snake_case and camelCase field names from backend responses. Update refreshTunnelMetrics to normalize metrics before setting state and explicitly cast active status to boolean.

desktop-client/src-tauri/src/lib.rs

@@ -665,6 +665,14 @@ pub fn run() {
             });
             refresh_tray_menu(app.handle());
 
+            let app_handle = app.handle().clone();
+            tauri::async_runtime::spawn(async move {
+                loop {
+                    refresh_tray_menu(&app_handle);
+                    tauri::async_runtime::sleep(std::time::Duration::from_secs(5)).await;
+                }
+            });
+
             Ok(())
         })
         .on_window_event(|window, event| match event {