fix(ns): class_exists() must use FQCN after PSR-4

Bare class_exists('Balance') looks up global Balance, always false
under AKSRT\* namespaces → REST 403 on balance exchange and friends.
Rewrite string checks to AKSRT\{Domain}\{Class}.

src/AKSRT/Forum/Forum.php

@@ -89,7 +89,7 @@ class Forum {
     private function draft_service(): DraftService {
         if (!$this->draft_svc) {
             // Draft service is loaded by bootstrap before this class.
-            if (!class_exists('DraftService', false)) {
+            if (!class_exists('AKSRT\\Forum\\DraftService', false)) {
                 require_once __DIR__ . '/class-aksrt-forum-draft-service.php';
             }
             $this->draft_svc = new DraftService($this);

src/AKSRT/Forum/PlateFollowPay.php

@@ -572,7 +572,7 @@ class PlateFollowPay {
     }
 
     private function is_follow_pay_enabled(int $plate_id): bool {
-        if (class_exists('Forum') && method_exists('Forum', 'is_plate_follow_pay_enabled')) {
+        if (class_exists('AKSRT\\Forum\\Forum') && method_exists('AKSRT\\Forum\\Forum', 'is_plate_follow_pay_enabled')) {
             return (bool) Forum::get_instance()->is_plate_follow_pay_enabled($plate_id);
         }
         return (int) get_post_meta($plate_id, '_aksrt_follow_pay', true) === 1;
@@ -582,7 +582,7 @@ class PlateFollowPay {
      * @return array{amount:float,modo:string,is_vip_price:bool,is_free:bool,label:string,base:float,vip_level:int}
      */
     private function resolve_price(int $plate_id, int $user_id): array {
-        if (class_exists('Forum') && method_exists('Forum', 'resolve_plate_follow_pay_price')) {
+        if (class_exists('AKSRT\\Forum\\Forum') && method_exists('AKSRT\\Forum\\Forum', 'resolve_plate_follow_pay_price')) {
             return Forum::get_instance()->resolve_plate_follow_pay_price($plate_id, $user_id);
         }
         return [
@@ -604,7 +604,7 @@ class PlateFollowPay {
             return function_exists('aksrt_guest_has_plate_follow_access')
                 && aksrt_guest_has_plate_follow_access($plate_id);
         }
-        if (class_exists('Forum') && method_exists('Forum', 'is_user_following_plate')) {
+        if (class_exists('AKSRT\\Forum\\Forum') && method_exists('AKSRT\\Forum\\Forum', 'is_user_following_plate')) {
             return (bool) Forum::get_instance()->is_user_following_plate($user_id, $plate_id);
         }
         $follow_list = get_user_meta($user_id, 'aksrt_follow_plate', true);
@@ -615,7 +615,7 @@ class PlateFollowPay {
     }
 
     private function mark_followed(int $user_id, int $plate_id): void {
-        if (class_exists('Forum') && method_exists('Forum', 'mark_plate_followed')) {
+        if (class_exists('AKSRT\\Forum\\Forum') && method_exists('AKSRT\\Forum\\Forum', 'mark_plate_followed')) {
             Forum::get_instance()->mark_plate_followed($user_id, $plate_id);
             return;
         }

src/AKSRT/Forum/PlateMetaBox.php

@@ -59,7 +59,7 @@ class PlateMetaBox {
         $roles_map     = [];
         $applications  = [];
 
-        if (class_exists('Forum')) {
+        if (class_exists('AKSRT\\Forum\\Forum')) {
             $forum         = Forum::get_instance();
             $moderator_ids = $forum->get_plate_moderators($plate_id);
             $roles_map     = $forum->get_moderator_roles($plate_id);
@@ -292,7 +292,7 @@ class PlateMetaBox {
             if ($status === 'pending') {
                 return true;
             }
-            return class_exists('Forum') && $status === Forum::APPLICATION_PENDING;
+            return class_exists('AKSRT\\Forum\\Forum') && $status === Forum::APPLICATION_PENDING;
         }));
         if (!$pending) {
             echo '<p class="description">' . esc_html__('暂无待处理申请。', 'aksrt') . '</p>';
@@ -495,7 +495,7 @@ class PlateMetaBox {
             $desired[$add_id] = $add_role;
         }
 
-        if (class_exists('Forum')) {
+        if (class_exists('AKSRT\\Forum\\Forum')) {
             $forum   = Forum::get_instance();
             $current = $forum->get_plate_moderators($post_id);
             foreach ($current as $uid) {
@@ -527,7 +527,7 @@ class PlateMetaBox {
         $actions = isset($_POST['aksrt_plate_app']) && is_array($_POST['aksrt_plate_app'])
             ? wp_unslash($_POST['aksrt_plate_app'])
             : [];
-        if (!$actions || !class_exists('Forum')) {
+        if (!$actions || !class_exists('AKSRT\\Forum\\Forum')) {
             return;
         }
 

src/AKSRT/Forum/TopicPay.php

@@ -576,7 +576,7 @@ class TopicPay {
      * @return array{amount:float,is_vip_price:bool,is_free:bool,label:string,base:float,vip_set:bool,vip_level:int}
      */
     private function resolve_price(int $topic_id, int $user_id): array {
-        if (class_exists('Forum')) {
+        if (class_exists('AKSRT\\Forum\\Forum')) {
             return Forum::get_instance()->resolve_topic_pay_price($topic_id, $user_id);
         }
         return [
@@ -594,7 +594,7 @@ class TopicPay {
         if ($user_id <= 0) {
             return function_exists('aksrt_guest_has_paid_access') && aksrt_guest_has_paid_access($topic_id);
         }
-        if (class_exists('Forum')) {
+        if (class_exists('AKSRT\\Forum\\Forum')) {
             return Forum::get_instance()->has_user_paid_topic($user_id, $topic_id);
         }
         if (class_exists('\AKSRT\Payment\Order')) {
@@ -608,7 +608,7 @@ class TopicPay {
     }
 
     private function mark_unlocked(int $user_id, int $topic_id): void {
-        if (class_exists('Forum') && method_exists('Forum', 'mark_topic_unlocked')) {
+        if (class_exists('AKSRT\\Forum\\Forum') && method_exists('AKSRT\\Forum\\Forum', 'mark_topic_unlocked')) {
             Forum::get_instance()->mark_topic_unlocked($user_id, $topic_id);
             return;
         }