feat(import): 엑셀 불러오기 미리보기에 전체 교각의 입력값 표시

- 교각 정보: 교각마다 열 하나, 행은 형식·EL·기초·말뚝·두부보·기둥·받침/IP 수·불러오기 여부
- 받침과 IP: 모든 교각을 한 표에 두고 교각 열을 추가, 표는 스크롤
- 교각 이름 클릭으로 미리볼 교각을 고르던 방식은 제거 (전체를 보여 줌)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

index.html

@@ -291,17 +291,21 @@
             <h3>미리보기</h3>
             <p id="preview-title" class="muted"></p>
             <h4>교각 정보</h4>
-            <table id="pv-pier" class="grid-table"><tbody></tbody></table>
+            <div class="pv-scroll"><table id="pv-pier" class="grid-table"></table></div>
             <h4>받침</h4>
-            <table id="pv-bearings" class="grid-table">
-              <thead><tr><th>번호</th><th>x (m)</th><th>y (m)</th><th>z (m)</th><th>방위각</th><th>위치</th></tr></thead>
-              <tbody></tbody>
-            </table>
+            <div class="pv-scroll">
+              <table id="pv-bearings" class="grid-table">
+                <thead><tr><th>교각</th><th>번호</th><th>x (m)</th><th>y (m)</th><th>z (m)</th><th>방위각</th><th>위치</th></tr></thead>
+                <tbody></tbody>
+              </table>
+            </div>
             <h4>IP</h4>
-            <table id="pv-ips" class="grid-table">
-              <thead><tr><th>점</th><th>x (m)</th><th>y (m)</th><th>꺾임각</th></tr></thead>
-              <tbody></tbody>
-            </table>
+            <div class="pv-scroll">
+              <table id="pv-ips" class="grid-table">
+                <thead><tr><th>교각</th><th>점</th><th>x (m)</th><th>y (m)</th><th>꺾임각</th></tr></thead>
+                <tbody></tbody>
+              </table>
+            </div>
           </section>
         </div>
       </div>