[Feature]: 现在的在线更新在前台做的，会导致更新期间应用不可用，希望改成后台更新

## Summary

## Problem / Motivation

现在的在线更新在前台做的，会导致更新期间应用不可用

## Proposed Solution

希望改成后台更新，更新好提醒安装

## Additional Context

2.2 beta3

Start by locating the online-update entry point and tracing how the current foreground update runs. Verify that normal application use remains available while the update is prepared, and that completion triggers an installation prompt; done means this behavior is covered by the relevant update tests, if present.

Vom Indexierungsmodell aus dem Issue-Text verfasst.