🎨 Palette: EventList RowView의 키보드 접근성 및 시맨틱 향상

[seonghobae]

💡 What: EventList 컴포넌트 내부의 RowView 버튼에 focus-visible 스타일과 aria-current, aria-expanded 속성을 추가했습니다.
🎯 Why: 타임라인에서 이벤트를 키보드로 탐색할 때 현재 포커스된 위치를 시각적으로 알 수 없었으며, 스크린 리더 사용자에게 현재 선택된 이벤트인지, 하위 항목이 펼쳐져 있는지에 대한 상태 정보가 부족했습니다.
📸 Before/After: 키보드 Tab 이동 시 링이 올바르게 표시됩니다.
♿ Accessibility:

• 명시적인 포커스 표시 (focus-visible:ring-2)
• 현재 항목 표시 (aria-current="step")
• 확장 가능 영역 상태 제공 (aria-expanded)

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PR created automatically by Jules for task 17560178948129585111 started by @seonghobae

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