🎨 Palette: Overview stats 토글 버튼 키보드 포커스 접근성 개선

[seonghobae]

overview-stats 컴포넌트의 설명 텍스트를 펼치거나 접는 버튼에 키보드 포커스 스타일이 누락되어 있어, 키보드 내비게이션 사용자에게 현재 포커스 위치를 명확히 보여주지 못하는 문제를 수정했습니다.

Tailwind CSS의 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring rounded-sm 클래스를 추가하여 탭(Tab) 키 이동 시 포커스 링이 보이도록 접근성을 개선했습니다.

---

PR created automatically by Jules for task 1138085163110647654 started by @seonghobae

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.