added contract history

frontend/src/pages/contracts/ContractDetail.tsx

@@ -3,7 +3,7 @@ import { useParams, Link, useNavigate, useLocation } from 'react-router-dom';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { contractApi, uploadApi, meterApi, contractTaskApi, appSettingsApi } from '../../services/api';
 import { ContractEmailsSection } from '../../components/email';
-import { ContractDetailModal } from '../../components/contracts';
+import { ContractDetailModal, ContractHistorySection } from '../../components/contracts';
 import InvoicesSection from '../../components/contracts/InvoicesSection';
 import { useAuth } from '../../context/AuthContext';
 import Card from '../../components/ui/Card';
@@ -2683,6 +2683,14 @@ export default function ContractDetail() {
         </Card>
       )}
 
+      {/* Vertragshistorie (nur für Mitarbeiter) */}
+      {!isCustomerPortal && hasPermission('contracts:read') && (
+        <ContractHistorySection
+          contractId={contractId}
+          canEdit={hasPermission('contracts:update')}
+        />
+      )}
+
       {/* Vorgängervertrag Modal */}
       {showPredecessorModal && c.previousContract && (
         <ContractDetailModal