Phase 0.3: migrate date formatting to date-fns

frontend/src/components/dms/FilePreviewModal.tsx

@@ -8,6 +8,7 @@ import React, { useEffect, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Modal } from '@/components/ui/Modal';
 import { Button } from '@/components/ui/Button';
+import { formatDateShort } from '@/utils/date';
 import { Badge } from '@/components/ui/Badge';
 import { getFilePreviewUrl, type DmsFile } from '@/api/dms';
 import { FileText } from 'lucide-react';
@@ -56,7 +57,7 @@ export function FilePreviewModal({ open, file, onClose }: FilePreviewModalProps)
           <span className="text-sm text-secondary-500">{formatFileSize(file.size_bytes ?? file.size ?? 0)}</span>
           {file.created_at && (
             <span className="text-sm text-secondary-500">
-              {t('dms.fileModified')}: {new Date(file.created_at).toLocaleDateString()}
+              {t('dms.fileModified')}: {formatDateShort(file.created_at)}
             </span>
           )}
         </div>