Memoize dashboard and history table columns

frontend/src/components/BanTable.tsx

@@ -8,6 +8,7 @@
  * Columns: Time, IP, Service, Country, Jail, Ban Count.
  */
 
+import { useMemo } from "react";
 import {
   Badge,
   Button,
@@ -194,7 +195,7 @@ export function BanTable({ timeRange, origin = "all", source = "fail2ban" }: Ban
   const styles = useStyles();
   const { banItems, total, page, setPage, loading, error, refresh } = useBans(timeRange, origin, source);
 
-  const banColumns = buildBanColumns(styles);
+  const banColumns = useMemo(() => buildBanColumns(styles), [styles]);
 
   // --------------------------------------------------------------------------
   // Loading state