修复: GET /v1/admin/promo/price/list 字段不匹配导致 400

前端发 rule_id/subscribe_id (均可选), 后端 API 定义为 promo_rule_id
(required), 直接返回 "PromoRuleId is a required field"。

对齐前端约定 (与 usage/list 命名一致):
- API: promo_rule_id(required) → rule_id + subscribe_id, 均可选
- model.QueryPriceList: 改为接 PriceFilter, 按条件过滤
- 同步 fake mock 与校验测试签名

apis/admin/promo.api

@@ -52,9 +52,10 @@ type (
 		Items       []PromoPriceItem `json:"items" validate:"required,min=1,dive"`
 	}
 	GetPromoPriceListRequest {
-		PromoRuleId int64 `form:"promo_rule_id" validate:"required,gt=0"`
 		Page        int64 `form:"page" validate:"required,gt=0"`
 		Size        int64 `form:"size" validate:"required,gt=0,lte=200"`
+		RuleId      int64 `form:"rule_id,omitempty"`
+		SubscribeId int64 `form:"subscribe_id,omitempty"`
 	}
 	GetPromoPriceListResponse {
 		Total int64        `json:"total"`