🐛 Fix(gui): make backgroundThrottling optional in window options type

#1435 removed `backgroundThrottling: false` from `defaultWebPreferences`, but
`IBrowserWindowOptions.webPreferences` still declared the field as required, so
`tsc` failed on all five window definitions.

Mark it optional rather than dropping it: omitting the field keeps Electron's
default (throttle when hidden), which is what #1435 intended, while individual
windows can still opt out explicitly if they ever need full-speed background
rendering.

src/universal/types/types.d.ts

@@ -144,7 +144,8 @@ interface IBrowserWindowOptions {
     nodeIntegration: boolean,
     nodeIntegrationInWorker: boolean,
     contextIsolation: boolean,
-    backgroundThrottling: boolean
+    // 不传即沿用 Electron 默认值（true，窗口不可见时降频）；仅在某个窗口确实需要后台全速渲染时才显式关闭。
+    backgroundThrottling?: boolean
     webSecurity?: boolean
   },
   vibrancy?: string | any,