🎨 Palette: 비동기 작업 버튼에 인라인 로딩 텍스트 피드백 추가

[seonghobae]

문서 업로드(submitDocument) 및 작업 재시도(retryActiveJob)와 같은 비동기 네트워크 작업을 수행할 때 버튼 텍스트를 로딩 상태로 변경하여 사용자에게 명확한 진행 피드백을 제공하는 UX 개선 사항입니다. 작업이 완료되거나 실패하면 finally 블록을 통해 버튼의 원래 HTML이 안전하게 복원됩니다. 프론트엔드 변경으로 인한 ViewerUiControllerTest의 문자열 검증 오류를 방지하기 위해 테스트 어설션을 업데이트했습니다.

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PR created automatically by Jules for task 2587046488421731529 started by @seonghobae

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