feat(forum): plate follow cash coupons + free auto-order

- Meta _aksrt_follow_pay_coupon_s + plate admin toggle (money only)
- Plate_Follow_Pay soft/hard coupon apply, free-after-discount, burn via shared helper
- Cashier auto-submits free topic/plate orders; topic coupon label no longer "预留"

inc/classes/forum/class-aksrt-plate-meta-box.php

@@ -190,6 +190,13 @@ class AKSRT_Plate_Meta_Box {
             <input type="number" step="0.01" min="0" class="widefat" name="aksrt_plate_follow_pay_vip2_price" id="aksrt_plate_follow_pay_vip2_price" value="<?php echo esc_attr((string) ($follow_pay['vip2_price'] ?? '')); ?>" placeholder="<?php esc_attr_e('留空=不设 VIP2 价；0=VIP2 免费', 'aksrt'); ?>">
             <span class="description"><?php esc_html_e('现金模式用元；积分模式填积分数。未填 VIP1 时仍可读旧「VIP 价格」字段。', 'aksrt'); ?></span>
         </p>
+        <p>
+            <label>
+                <input type="checkbox" name="aksrt_plate_follow_pay_coupon_s" value="1" <?php checked(!empty($follow_pay['coupon_s'])); ?>>
+                <?php esc_html_e('允许优惠码（仅现金关注）', 'aksrt'); ?>
+            </label>
+            <span class="description" style="display:block;"><?php esc_html_e('开启后收银台可输入优惠码；积分关注不吃券。', 'aksrt'); ?></span>
+        </p>
         <hr>
         <?php
     }
@@ -398,6 +405,7 @@ class AKSRT_Plate_Meta_Box {
             delete_post_meta($post_id, '_aksrt_follow_pay_vip_price');
             delete_post_meta($post_id, '_aksrt_follow_pay_vip1_price');
             delete_post_meta($post_id, '_aksrt_follow_pay_vip2_price');
+            delete_post_meta($post_id, '_aksrt_follow_pay_coupon_s');
             return;
         }
 
@@ -405,6 +413,7 @@ class AKSRT_Plate_Meta_Box {
         update_post_meta($post_id, '_aksrt_follow_pay_modo', $modo);
         update_post_meta($post_id, '_aksrt_follow_pay_price', $price);
         update_post_meta($post_id, '_aksrt_follow_pay_points', $points);
+        update_post_meta($post_id, '_aksrt_follow_pay_coupon_s', !empty($_POST['aksrt_plate_follow_pay_coupon_s']) ? 1 : 0);
 
         if (isset($_POST['aksrt_plate_follow_pay_vip1_price']) && (string) wp_unslash($_POST['aksrt_plate_follow_pay_vip1_price']) !== '') {
             $vip1 = max(0, (float) wp_unslash($_POST['aksrt_plate_follow_pay_vip1_price']));
@@ -424,7 +433,7 @@ class AKSRT_Plate_Meta_Box {
     }
 
     /**
-     * @return array{enabled:bool,modo:string,price:float,points:int,vip1_price:string,vip2_price:string}
+     * @return array{enabled:bool,modo:string,price:float,points:int,vip1_price:string,vip2_price:string,coupon_s:bool}
      */
     private function get_follow_pay_meta(int $plate_id): array {
         $enabled = (int) get_post_meta($plate_id, '_aksrt_follow_pay', true) === 1;
@@ -451,6 +460,7 @@ class AKSRT_Plate_Meta_Box {
             'points'     => (int) get_post_meta($plate_id, '_aksrt_follow_pay_points', true),
             'vip1_price' => $vip1_set ? (string) (float) $vip1_raw : '',
             'vip2_price' => $vip2_set ? (string) (float) $vip2_raw : '',
+            'coupon_s'   => (int) get_post_meta($plate_id, '_aksrt_follow_pay_coupon_s', true) === 1,
         ];
     }