Set default 6 per page

Update pagination to default to 6 items per page in Agents screen, preserving navigation controls and responsive layout.

src/pages/Agents.tsx

@@ -28,7 +28,7 @@ export default function Agents() {
   const [isCreateDialogOpen, setIsCreateDialogOpen] = useState(false);
   const [searchQuery, setSearchQuery] = useState("");
   const [currentPage, setCurrentPage] = useState(1);
-  const [itemsPerPage, setItemsPerPage] = useState(9);
+  const [itemsPerPage, setItemsPerPage] = useState(6);
 
   const [agents] = useState([
     {