feat: add dynamic tray menu with connection status, transfer metrics, and toggle action

Add TrayState struct to track menu items for status, received/sent bytes, and connection toggle. Add format_data_size helper to convert bytes to human-readable units (B, KB, MB, GB, TB). Add current_metrics, update_tray_menu, refresh_tray_menu, and toggle_tray_connection functions to manage tray state. Update tray menu to include status, received, sent, and toggle items. Call refresh_tray_menu after enroll_device

desktop-client/src/App.tsx

@@ -52,7 +52,7 @@ function currentProfileLabel(state: EnrollmentState | null) {
 
 function formatDataSize(bytes: number) {
   if (!bytes) {
-    return "0 MB";
+    return "0 B";
   }
 
   const units = ["B", "KB", "MB", "GB", "TB"];