refactor: 全新预设系统、插件系统，实现多模态支持高度可自定义化的 AI 助手 (Sourcery refactored)

[sourcery-ai]

Pull Request #755 refactored by Sourcery.

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re-run and update (force-push) this Pull Request with new refactorings as
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will be closed automatically.

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Help us improve this pull request!

[sourcery-ai]

Function QQRobotClient.on_at_message_create refactored with the following changes:

• Use f-string instead of string concatenation [×2] (use-fstring-for-concatenation)