fix(dashboard): 修正活动奖品分析成本口径

活动奖品分析接口统一使用 products.cost_price 计算 prizeValue、cost 和 totalCost，避免误用售价导致成本统计偏差。

internal/api/admin/dashboard_admin.go

@@ -1237,13 +1237,13 @@ func (h *handler) DashboardActivityPrizeAnalysis() core.HandlerFunc {
 			issueTotalWeights[r.IssueID] += int64(r.Weight)
 		}
 
-		// 4. 批量查询商品价格和名称 (Product Price and Name)
-		priceMap := make(map[int64]int64)
+		// 4. 批量查询商品成本价和名称 (Product Cost and Name)
+		productCostMap := make(map[int64]int64)
 		productNameMap := make(map[int64]string)
 		if len(productIDs) > 0 {
 			products, _ := h.readDB.Products.WithContext(ctx.RequestContext()).ReadDB().Where(h.readDB.Products.ID.In(productIDs...)).Find()
 			for _, p := range products {
-				priceMap[p.ID] = p.Price
+				productCostMap[p.ID] = p.CostPrice
 				productNameMap[p.ID] = p.Name
 			}
 		}
@@ -1306,7 +1306,7 @@ func (h *handler) DashboardActivityPrizeAnalysis() core.HandlerFunc {
 		for i, r := range rsAll {
 			dc := drawCounts[r.IssueID] // 该期的总抽奖数
 			wc := winCounts[r.ID]       // 该奖品的中奖数
-			price := priceMap[r.ProductID]
+			cost := productCostMap[r.ProductID]
 
 			issued := r.OriginalQty - r.Quantity
 
@@ -1332,7 +1332,7 @@ func (h *handler) DashboardActivityPrizeAnalysis() core.HandlerFunc {
 					}
 					return "虚拟/道具"
 				}(),
-				PrizeValue:        price,
+				PrizeValue:        cost,
 				TotalQuantity:     r.OriginalQty,
 				IssuedQuantity:    issued,
 				DrawCount:         dc,
@@ -1340,10 +1340,10 @@ func (h *handler) DashboardActivityPrizeAnalysis() core.HandlerFunc {
 				WinRate:           actual,
 				Probability:       prob,
 				ActualProbability: actual,
-				Cost:              price,
+				Cost:              cost,
 			}
 
-			totalCost += price * wc
+			totalCost += cost * wc
 			winRates = append(winRates, actual)
 		}