fix:법인도장 이미지를 base64 data URL로 반환 (local disk 404 해결)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

resources/views/esign/create.blade.php

@@ -245,7 +245,7 @@ className="w-full border border-gray-300 rounded-md px-2.5 py-1.5 text-sm focus:
                             </div>
                             {registeredStamp ? (
                                 <div className="flex items-center gap-3">
-                                    <img src={registeredStamp.image_url + '?t=' + Date.now()} alt="법인도장" className="h-16 w-16 object-contain border border-blue-300 rounded bg-white p-1" />
+                                    <img src={registeredStamp.image_url} alt="법인도장" className="h-16 w-16 object-contain border border-blue-300 rounded bg-white p-1" />
                                     <div className="flex-1">
                                         <p className="text-xs text-blue-700">등록된 법인도장이 자동 적용됩니다.</p>
                                         <a href="/esign#settings" className="text-[11px] text-blue-500 hover:underline">대시보드에서 변경</a>