Add an option to customize the app UI font

### Feature summary

Currently, there's an option to change the terminal font. It would be nice if there were also an option to change the app's UI font.

### What problem are you trying to solve?

It improves accessibility by letting users choose a font that's easier for them to read. It also lets users customize the app's appearance and makes the experience more consistent, since the terminal font can already be changed.

### Proposed solution

Add an option in the app's settings to let users choose the UI font, similar to the existing option for changing the terminal font.

### Workflow impact

Users who want better readability, accessibility, or a more personalized experience would benefit from this. It improves the app experience without changing the existing workflow, since it's an optional customization.

### Installation context

_No response_

### Additional context

_No response_

该 issue 未指定任何文件或测试。首先在应用设置中找到现有的终端字体设置，然后跟踪其选项的存储和应用方式；当用户可以在设置中选择单独的 UI 字体，并看到它在不改变终端字体选项的情况下得到一致应用时，即视为完成。

由索引模型根据 Issue 内容生成。