🎨 Palette: 접근성 향상을 위한 테이블 요소 및 다이얼로그 속성 추가

[seonghobae]

사용자 경험(UX) 및 접근성(a11y) 개선을 위해 대시보드 화면(scanner/dashboard/index.html)의 테이블 요소와 네이티브 HTML <dialog> 요소에 필요한 접근성 속성을 추가했습니다. 이 작업은 스크린 리더와 키보드 사용자 등 모든 사용자가 명확하게 상호작용할 수 있도록 돕습니다. 또한 이 학습 내용을 .Jules/palette.md 파일에 기록하였습니다.

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PR created automatically by Jules for task 6534264553721879662 started by @seonghobae

[google-labs-jules]

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