feat(pay): content cashier coupon and rebate discount chain

Wire zibll-style cash content discounts: VIP list price → buyer 推广折扣 → coupon, then commission on final pay. Reuse AKSRT_Coupon, add Invite::get_referrer, cashier UI, and paid-time coupon burn + rebate_log.

inc/classes/settings/class-aksrt-settings-credits-payment-groups.php

@@ -136,6 +136,15 @@ trait AKSRT_Settings_Credits_Payment_Groups {
         return AKSRT_Settings_Payment_Runtime::get_paid_content_settings();
     }
 
+    /**
+     * Content coupon global switches.
+     *
+     * @return array{enabled:bool,desc:string}
+     */
+    public static function get_content_coupon_settings(): array {
+        return AKSRT_Settings_Payment_Runtime::get_content_coupon_settings();
+    }
+
     /**
      * @return array{enabled:bool,mode:string,packages_raw:string,package_count:int,help_text:string}
      */

inc/classes/settings/class-aksrt-settings-home-cms.php

@@ -383,6 +383,10 @@ class AKSRT_Settings_Home_Cms {
         return AKSRT_Settings_Payment_Runtime::get_paid_content_settings();
     }
 
+    public static function get_content_coupon_settings(): array {
+        return AKSRT_Settings_Payment_Runtime::get_content_coupon_settings();
+    }
+
     public static function get_payment_recharge_settings(): array {
         return AKSRT_Settings_Payment_Runtime::get_payment_recharge_settings();
     }

inc/classes/settings/class-aksrt-settings-payment-runtime.php

@@ -72,6 +72,22 @@ class AKSRT_Settings_Payment_Runtime {
                 'remote_ext'   => sanitize_text_field((string) ($settings['payment_download_remote_ext'] ?? 'zip,rar,7z')),
                 'alone_page'   => !empty($settings['payment_down_alone_page']),
             ],
+            // Content cashier coupon (zibll coupon_post_s / coupon_desc).
+            'coupon_post_s'        => !empty($settings['coupon_post_s']),
+            'coupon_desc'          => sanitize_textarea_field((string) ($settings['coupon_desc'] ?? '')),
+        ];
+    }
+
+    /**
+     * Content coupon global switches (zibll coupon_post_s).
+     *
+     * @return array{enabled:bool,desc:string}
+     */
+    public static function get_content_coupon_settings(): array {
+        $settings = self::get_paid_content_settings();
+        return [
+            'enabled' => !empty($settings['coupon_post_s']),
+            'desc'    => (string) ($settings['coupon_desc'] ?? ''),
         ];
     }