feat(forum,admin): plate follow-pay MVP, sales column, order type tabs

Wire paid plate follow (admin meta + points/balance purchase + AJAX),
re-check plate gate on topics, post list sales column, and order type
subtabs; update gap matrix and admin IA map.

docs/admin-ia-map.md

@@ -27,6 +27,7 @@ Do **not** reintroduce operational workbenches into the SPA once native pages sh
 支付中心 (aksrt_pay)                         pos ~36–38, dashicons-cart
 ├─ 概览              aksrt_pay
 ├─ 订单              aksrt_orders
+├─ 付费文章          aksrt_pay_products
 ├─ 发货及物流        aksrt_shipping
 ├─ 售后管理          aksrt_after_sale
 ├─ 优惠码            aksrt_coupons