修复(#79): 促销管理后台API + 审查问题修复

- 实现促销管理接口：规则CRUD、优惠价配置、使用记录查询
- 修复 UpsertPrices 新增记录时提前 return 的问题
- DeleteRule/DeletePrice 不存在记录返回 code=404
- SetPromoPriceRequest.items 空数组校验
- 分页参数限制 page>0、1<=size<=200
- 下单侧促销价格按数量档总价口径计算（含 #87 修复）

Co-authored-by: multica-agent <github@multica.ai>

internal/logic/admin/promo/setPriceLogic.go

@@ -0,0 +1,81 @@
+package promo
+
+import (
+	"context"
+
+	promomodel "github.com/perfect-panel/server/internal/model/promo"
+	subscribeModel "github.com/perfect-panel/server/internal/model/subscribe"
+	"github.com/perfect-panel/server/internal/svc"
+	"github.com/perfect-panel/server/internal/types"
+	"github.com/perfect-panel/server/pkg/logger"
+	"github.com/perfect-panel/server/pkg/xerr"
+	"github.com/pkg/errors"
+)
+
+type SetPriceLogic struct {
+	logger.Logger
+	ctx    context.Context
+	svcCtx *svc.ServiceContext
+}
+
+func NewSetPriceLogic(ctx context.Context, svcCtx *svc.ServiceContext) *SetPriceLogic {
+	return &SetPriceLogic{
+		Logger: logger.WithContext(ctx),
+		ctx:    ctx,
+		svcCtx: svcCtx,
+	}
+}
+
+func (l *SetPriceLogic) SetPrice(req *types.SetPromoPriceRequest) error {
+	if _, err := l.svcCtx.PromoModel.FindRule(l.ctx, req.PromoRuleId); err != nil {
+		l.Errorw("[SetPromoPrice] Find Rule Error", logger.Field("error", err.Error()))
+		return errors.Wrapf(xerr.NewErrCode(xerr.DatabaseQueryError), "find promo rule error: %v", err.Error())
+	}
+	subscribeIds := make([]int64, 0, len(req.Items))
+	seenSubscribeIds := make(map[int64]struct{}, len(req.Items))
+	for _, item := range req.Items {
+		if _, ok := seenSubscribeIds[item.SubscribeId]; ok {
+			continue
+		}
+		seenSubscribeIds[item.SubscribeId] = struct{}{}
+		subscribeIds = append(subscribeIds, item.SubscribeId)
+	}
+	var subscribes []*subscribeModel.Subscribe
+	if err := l.svcCtx.DB.WithContext(l.ctx).Model(&subscribeModel.Subscribe{}).Where("id IN ?", subscribeIds).Find(&subscribes).Error; err != nil {
+		l.Errorw("[SetPromoPrice] Find Subscribe Error", logger.Field("error", err.Error()))
+		return errors.Wrapf(xerr.NewErrCode(xerr.DatabaseQueryError), "find subscribe error: %v", err.Error())
+	}
+	subscribeById := make(map[int64]*subscribeModel.Subscribe, len(subscribes))
+	for _, sub := range subscribes {
+		subscribeById[sub.Id] = sub
+	}
+	items := make([]*promomodel.SubscribePromo, 0, len(req.Items))
+	cacheKeys := make([]string, 0, len(req.Items))
+	for _, item := range req.Items {
+		sub, ok := subscribeById[item.SubscribeId]
+		if !ok {
+			return errors.Wrapf(xerr.NewErrCode(xerr.InvalidParams), "subscribe plan not found")
+		}
+		originPrice := sub.UnitPrice * item.Quantity
+		if item.PromoPrice >= originPrice {
+			return errors.Wrapf(xerr.NewErrCode(xerr.InvalidParams), "promo_price must be less than unit_price * quantity")
+		}
+		items = append(items, &promomodel.SubscribePromo{
+			SubscribeId: item.SubscribeId,
+			PromoRuleId: req.PromoRuleId,
+			Quantity:    item.Quantity,
+			PromoPrice:  item.PromoPrice,
+		})
+		cacheKeys = append(cacheKeys, subscribePromoCacheKey(item.SubscribeId))
+	}
+	if err := l.svcCtx.PromoModel.UpsertPrices(l.ctx, req.PromoRuleId, items); err != nil {
+		l.Errorw("[SetPromoPrice] Database Error", logger.Field("error", err.Error()))
+		return errors.Wrapf(xerr.NewErrCode(xerr.DatabaseUpdateError), "set promo price error: %v", err.Error())
+	}
+	if len(cacheKeys) > 0 {
+		if err := l.svcCtx.Redis.Del(l.ctx, cacheKeys...).Err(); err != nil {
+			l.Errorw("[SetPromoPrice] Delete Cache Error", logger.Field("error", err.Error()))
+		}
+	}
+	return nil
+}