fix(shutdown): mark shutdown as exiting to stop background tasks (#5024)

* fix(shutdown): mark shutdown as exiting to stop background tasks

- lib.rs:570 → Flag app as exiting on ExitRequested, notify proxy guard, start cleanup immediately, with fallback in Exit event
- tray/mod.rs:190 → Add unified exit checks around tray init/updates to prevent UI recreation during shutdown
- event_driven_proxy.rs:252 → Ensure proxy guard skips all restore/re-enable work (including sysproxy.exe calls) once exit flag is set

* fix(shutdown): refine exit handling and proxy guard notifications

* fix(shutdown): add guard to run shutdown routine only once per lifecycle

src-tauri/src/feat/window.rs

@@ -1,12 +1,9 @@
+use crate::config::Config;
+use crate::core::event_driven_proxy::EventDrivenProxyManager;
+use crate::core::{CoreManager, handle, sysopt};
 use crate::utils;
 use crate::utils::window_manager::WindowManager;
-use crate::{
-    config::Config,
-    core::{CoreManager, handle, sysopt},
-    logging,
-    module::lightweight,
-    utils::logging::Type,
-};
+use crate::{logging, module::lightweight, utils::logging::Type};
 
 /// Public API: open or close the dashboard
 pub async fn open_or_close_dashboard() {
@@ -27,6 +24,7 @@ pub async fn quit() {
     // 获取应用句柄并设置退出标志
     let app_handle = handle::Handle::app_handle();
     handle::Handle::global().set_is_exiting();
+    EventDrivenProxyManager::global().notify_app_stopping();
 
     // 优先关闭窗口，提供立即反馈
     if let Some(window) = handle::Handle::get_window() {