feat(badges): boot auto-award + checkin hook + search history slot

Wire BadgeAutoAward/Badges init, fire aksrt_checkin_done, and optional
search-history mount point on the search widget.

src/AKSRT/Credits/Signin.php

@@ -168,6 +168,7 @@ class Signin {
         update_user_meta($user_id, 'checkin_all_day', $all_day); // zibll alias
         update_user_meta($user_id, 'aksrt_checkin_continuous_day', $new_streak);
         update_user_meta($user_id, 'checkin_continuous_day', $new_streak); // zibll alias
+        do_action('aksrt_checkin_done', $user_id);
 
         return new \WP_REST_Response([
             'success' => true,