Update Pier_v1 project

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

index.html

@@ -24,7 +24,6 @@
           <span id="save-status" class="savest">저장 전</span>
           <button id="home-from-app" class="btn-s" type="button" hidden>홈으로</button>
           <button id="save-project" class="btn-s" type="button" disabled title="프로젝트 파일 저장 (Ctrl+S)">저장</button>
-          <button id="open-import" class="btn-s" type="button">엑셀 불러오기</button>
           <button id="open-project" class="btn-s" type="button">프로젝트 열기</button>
           <button id="regen" class="btn-p" type="button" disabled>선택 교각 형상 생성</button>
           <input id="project-file" type="file" accept=".json" hidden />