feat(forum): P1 topic coupons, P2 plate follow gateway, cash creator revenue

- Topic_Pay: soft/hard coupon validate, payable amount, free-after-discount, paid burn
- Creator_Revenue: settle content/topic/plate_follow cash (type=order), keep shop path
- Plate VIP1/VIP2 meta + resolve_plate_follow_pay_price via aksrt_get_user_vip_level
- New AKSRT_Plate_Follow_Pay REST multi-gateway; remove Credits×100 money bypass
- Frontend: cms-download plate_follow apiKind + forum-governance money cashier bridge

functions.php

@@ -180,6 +180,9 @@ if (class_exists('AKSRT_Content_Pay')) {
 if (class_exists('AKSRT_Topic_Pay')) {
     AKSRT_Topic_Pay::get_instance()->init();
 }
+if (class_exists('AKSRT_Plate_Follow_Pay')) {
+    AKSRT_Plate_Follow_Pay::get_instance()->init();
+}
 if (class_exists('AKSRT_Vip_Service')) {
     AKSRT_Vip_Service::get_instance()->init();
 }