Codeigniter 4 ajax post results in 404 error

I am trying to handle a form submit using the JQuery ajax function on localhost xampp. However, the following always results in a 404 page not found error:

Code:

$(document).on("click", ".iconsTop .iconst", function (e) {
    var idfilter = $(this).attr("id");;
    $.ajax({
      type: "POST",
      dataType: "text",
      url: "filter",
      data: { filter_id:idfilter },
      cache: false,
      success: function (data) {
        $('.maincontact').empty().append(data);
      }
    });
  });

Controller:

PHP Code:

class App_home extends BaseController
{
    public function filter()
    {
        echo 'ok';
    }
} 


Router

PHP Code:

use CodeIgniter\Router\RouteCollection;
$routes->setAutoRoute(true);
$routes->get('filter', 'App_home::filter'); 


After submitting the form, I always get the following error in Google Chrome's page inspector:

jquery-3.7.1.min.js:2 POST http://localhost/app/public/filter 404 (Not Found)

404 Controller or its method is not found: Filter::index