feat(订单): 实现推荐奖励系统支持佣金和赠送天数两种模式

重构推荐奖励处理逻辑，新增支持根据配置选择佣金奖励或赠送天数奖励
修改Discount相关字段类型为float64以支持小数折扣
添加GiftDays配置项控制赠送天数
新增FindActiveSubscribe方法查询用户有效订阅

internal/types/types.go

@@ -1170,6 +1170,7 @@ type InviteConfig struct {
 	ForcedInvite       bool  `json:"forced_invite"`
 	ReferralPercentage int64 `json:"referral_percentage"`
 	OnlyFirstPurchase  bool  `json:"only_first_purchase"`
+	GiftDays           int64 `json:"gift_days"`
 }
 
 type KickOfflineRequest struct {
@@ -2065,8 +2066,8 @@ type SubscribeConfig struct {
 }
 
 type SubscribeDiscount struct {
-	Quantity int64 `json:"quantity"`
-	Discount int64 `json:"discount"`
+	Quantity int64   `json:"quantity"`
+	Discount float64 `json:"discount"`
 }
 
 type SubscribeGroup struct {