fix(auth): use restUrl for modal-login under plain permalinks

Local WP has empty permalink_structure so /wp-json/* 404s on Apache.
modal-auth fell back to /wp-json/aksrt/v1; prefer aksrtData.restUrl
(index.php?rest_route=/aksrt/v1) and join paths correctly.

assets/js/follow.js

@@ -8,7 +8,11 @@
 (function () {
   'use strict';
 
-  var API_ROOT = (window.aksrtData && window.aksrtData.apiUrl) || '/wp-json/aksrt/v1';
+  var API_ROOT = (function () {
+    var d = window.aksrtData || {};
+    var raw = d.apiUrl || d.restUrl || d.rest_url || '/index.php?rest_route=/aksrt/v1';
+    return String(raw).replace(/\/$/, '');
+  })();
   var NONCE    = (window.aksrtData && window.aksrtData.restNonce) || '';
 
   function initFollowButtons() {