Check and improve accessibility with lighthouse

## Acceptance Criteria

- [ ] A Lighthouse accessibility audit is conducted and achieves above 80 on Accessibility.
- [ ] The Lighthouse report (HTML) is included in the Pull Request.
- [ ] CSS provides clear focus states to visually indicate the currently active control.
- [ ] All website controls can be navigated and activated using only the keyboard.

Check out the resources section below to figure out how to implement this requirement.

## Guidance 🧭

**Lighthouse Accessibility Testing:** [https://supercooldesign.co.uk/blog/how-to-run-a-lighthouse-audit](https://supercooldesign.co.uk/blog/how-to-run-a-lighthouse-audit)

首先对网站运行 Lighthouse 可访问性审计并检查报告的问题，然后检查控件及其 CSS，确认键盘导航和可见的焦点状态。完成标准是 Accessibility 分数高于 80、所有控件都支持键盘操作、焦点样式清晰，并在 pull request 中包含 HTML Lighthouse 报告。

由索引模型根据 Issue 内容生成。