fix(adminfront): fix ReferenceErrors and null checks in UI components

- Import and initialize 'navigate' in TenantUsersPage and TenantAdminsAndOwnersTab.
- Use optional chaining for 'user.id' in UserDetailPage to prevent runtime errors during initial load.

adminfront/src/features/tenants/routes/TenantUsersPage.tsx

@@ -9,7 +9,7 @@ import {
   UserMinus,
   UserPlus,
 } from "lucide-react";
-import { Link, useParams } from "react-router-dom";
+import { Link, useNavigate, useParams } from "react-router-dom";
 import { Badge } from "../../../components/ui/badge";
 import { Button } from "../../../components/ui/button";
 import {
@@ -38,6 +38,7 @@ import { t } from "../../../lib/i18n";
 
 function TenantUsersPage() {
   const params = useParams<{ tenantId: string }>();
+  const navigate = useNavigate();
   const tenantId = params.tenantId ?? "";
   const queryClient = useQueryClient();