feat: persist Tauri window state (#2377)

Add the window-state plugin and explicitly save size and position across app exit, restart, and lightweight-mode transitions.

src-tauri/src/commands/settings.rs

@@ -42,6 +42,8 @@ pub async fn save_settings(settings: crate::settings::AppSettings) -> Result<boo
 /// 重启应用程序（当 app_config_dir 变更后使用）
 #[tauri::command]
 pub async fn restart_app(app: AppHandle) -> Result<bool, String> {
+    crate::save_window_state_before_exit(&app);
+
     // 在后台延迟重启，让函数有时间返回响应
     tauri::async_runtime::spawn(async move {
         tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;