feat: restructure navigation, customize list columns, and move action buttons to search bar

1. Restructured navigation hierarchy (Hardware, Software, Ops Support, etc.).
2. Customized table columns for all asset categories according to new specs.
3. Moved Template/Upload/Export/Add buttons to search bar with layout optimization.
4. Hidden Asset Code and Previous User from list views (Modal only).
5. Added Current/Previous User and detailed PC spec fields (GPU, HDD3/4).

index.html

@@ -37,19 +37,7 @@
           <button id="btn-open-guide-header" class="btn btn-outline" title="프로세스 가이드">
             <i data-lucide="book-open"></i> 가이드
           </button>
-          <button id="btn-download-template" class="btn btn-outline" title="통합 양식 다운로드">
-            <i data-lucide="download"></i> 양식
-          </button>
-          <label for="excel-upload" class="btn btn-outline" title="엑셀 파일 업로드">
-            <i data-lucide="upload"></i> 업로드
-          </label>
           <input type="file" id="excel-upload" accept=".xlsx, .xls" style="display: none;" />
-          <button id="btn-export-excel" class="btn btn-primary" title="일괄 엑셀 저장">
-            <i data-lucide="file-spreadsheet"></i> 엑셀저장
-          </button>
-          <button id="btn-add-asset" class="btn btn-primary hidden">
-            <i data-lucide="plus"></i> 자산추가
-          </button>
         </div>
       </div>
     </header>