complete new audit system

frontend/src/components/contracts/InvoicesSection.tsx

@@ -1,5 +1,6 @@
 import { useState, useRef } from 'react';
 import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { formatDate } from '../../utils/dateFormat';
 import { Plus, Edit, Trash2, ChevronDown, ChevronUp, FileText, Download, AlertTriangle, Check, Eye } from 'lucide-react';
 import Modal from '../ui/Modal';
 import Button from '../ui/Button';
@@ -93,7 +94,7 @@ export default function InvoicesSection({
       {/* Collapsed view - show latest invoice */}
       {!isExpanded && sortedInvoices.length > 0 && (
         <div className="text-sm text-gray-600">
-          Letzte: {new Date(sortedInvoices[0].invoiceDate).toLocaleDateString('de-DE')} - {invoiceTypeLabels[sortedInvoices[0].invoiceType]}
+          Letzte: {formatDate(sortedInvoices[0].invoiceDate)} - {invoiceTypeLabels[sortedInvoices[0].invoiceType]}
         </div>
       )}
 
@@ -108,7 +109,7 @@ export default function InvoicesSection({
               <div className="flex items-center gap-4">
                 <div>
                   <div className="text-sm font-medium">
-                    {new Date(invoice.invoiceDate).toLocaleDateString('de-DE')}
+                    {formatDate(invoice.invoiceDate)}
                   </div>
                   <div className="text-xs text-gray-500">
                     {invoiceTypeLabels[invoice.invoiceType]}