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"

docs/zibll-gap-matrix.md

@@ -100,7 +100,7 @@ Note: zibll「商品管理」`zibpay_product_page` is **paid article sales**, no
 | 3 users.php submenus | done |
 | 4 SPA strip | done (ops routes redirect to native) |
 | 5+ behavior parity | done — native ops shell + plate follow-pay + topic pay matrix + multi-gateway topic cashier (`AKSRT_Topic_Pay` /pay/topic) + topic coupon burn (P1) + plate follow VIP1/2 + multi-gateway (`AKSRT_Plate_Follow_Pay` /pay/plate-follow) + cash creator revenue (content/topic/plate) + sales report/download logs + hidecontent + users commerce + order filters/clear-closed + post pay_type filter + bulk content-pay edit + income/rebate user filter |
-| 5 remaining | optional polish only (plate coupons, guest topic/plate purchase — out of scope); order note JSON preserve + shared coupon burn helper done |
+| 5 remaining | optional polish only (guest topic/plate purchase — out of scope); plate follow coupons + free auto-order + note JSON preserve + shared coupon burn done |
 
 ## Dual-UI rule