fix: handle deferred game database loading in library sidebar

[fishyy119]

修复程序启动后游戏列表不加载的问题。

该问题与 #551 引入的数据库分阶段加载相关，其虽然在主页的内容显示区订阅了加载完成状态，但是左侧的游戏列表没有订阅该状态，导致数据库加载完成后列表没有重新渲染。

较为有趣的是，在开发模式下使用大规模的游戏数据库未能复现该问题，推测可能是某处未知的状态更新触发了列表的重渲染；换为规模较小的游戏数据库才成功复现。

Fix #576

[Copilot]

Pull request overview

Adds a loading state to the Library sidebar so the game list UI is deferred until the background (phase 2) game database load completes, addressing the startup case where the list appears empty/not loaded.

Changes:

• Subscribe to gamesLoaded from useGameRegistry and gate Librarybar rendering on it.
• Show a spinner + localized “Loading games…” message while games are still loading.
• Add react-i18next translation usage for the loading message.

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