feat: [approval] 결재서명란에 참조자 표시 추가

- 결재 테이블 하단에 참조자 녹색 칩 표시
- reference step_type 필터링하여 존재 시에만 표시

resources/views/approvals/partials/_approval-stamp-table.blade.php

@@ -81,3 +81,17 @@
         </tr>
     </tbody>
 </table>
+
+@php
+    $refSteps = $approval->steps->where('step_type', 'reference')->values();
+@endphp
+@if($refSteps->count() > 0)
+<div style="margin-top: 8px; display: flex; align-items: center; gap: 6px; flex-wrap: wrap;">
+    <span style="font-size: 12px; font-weight: 600; color: #059669; white-space: nowrap;">참조</span>
+    @foreach($refSteps as $ref)
+        <span style="display: inline-flex; align-items: center; padding: 2px 10px; background: #ecfdf5; border: 1px solid #a7f3d0; border-radius: 9999px; font-size: 12px; color: #065f46; white-space: nowrap;">
+            {{ $ref->approver_name ?? ($ref->approver?->name ?? '-') }}
+        </span>
+    @endforeach
+</div>
+@endif