feat(tray): add tooltip to tray icon for better user experience (#2417)

Co-authored-by: Copilot <copilot@github.com>

src-tauri/src/lib.rs

@@ -748,6 +748,7 @@ pub fn run() {
 
             // 构建托盘
             let mut tray_builder = TrayIconBuilder::with_id(tray::TRAY_ID)
+                .tooltip("CC Switch") // 鼠标悬停提示
                 .on_tray_icon_event(|tray, event| match event {
                     // 鼠标悬停/点击到托盘图标时，后台异步刷新用量缓存，
                     // 让用户下一次（或快速打开菜单的那一刻）看到较新的数字。