feat(identity): tip QR upload, metrics engine, comment moderate caps

Close identity 1:1 gaps after p1: user-center weixin/alipay tip QR
upload+save, AKSRT_User_Metrics counters for medal get_type and level
XP bridges, forum/revenue/signin hooks, comment moderate via user_caps,
and clearer free-task deep links/status CTAs.

inc/classes/class-aksrt-signin.php

@@ -130,6 +130,8 @@ class AKSRT_Signin {
             return new WP_Error('aksrt_signin_dup', __('签到失败', 'aksrt'), ['status' => 409]);
         }
 
+        do_action('aksrt_user_signed_in', $user_id);
+
         if ($reward > 0) {
             if (class_exists('AKSRT_Points_Free')) {
                 $granted = AKSRT_Points_Free::grant_amount($user_id, $reward, 'sign_in', ['type' => 'user', 'id' => $user_id]);