fix: 将通知头像存储在缓存文件中，通过LRU缓存维护头像缓存数量，点击通知后可以跳转到对应的会话窗口(fixes #654)

electron/windows/notificationWindow.ts

@@ -27,6 +27,14 @@ export function destroyNotificationWindow() {
   }
   lastNotificationData = null;
 
+  // Linux:关闭通知服务并清理缓存（fire-and-forget，不阻塞退出）
+  if (isLinux && linuxNotificationService) {
+    linuxNotificationService.shutdownLinuxNotificationService().catch((error) => {
+      console.warn("[NotificationWindow] Failed to shutdown Linux notification service:", error);
+    });
+    linuxNotificationService = null;
+  }
+
   if (!notificationWindow || notificationWindow.isDestroyed()) {
     notificationWindow = null;
     return;