重构: 店铺套餐分配系统从加价模式改为返佣模式

主要变更：
- 重构分配模型：从加价模式（pricing_mode/pricing_value）改为返佣模式（base_commission + tier_commission）
- 删除独立的 my_package 接口，统一到 /api/admin/packages（通过数据权限自动过滤）
- 新增批量分配和批量调价功能，支持事务和性能优化
- 新增配置版本管理，订单创建时锁定返佣配置
- 新增成本价历史记录，支持审计和纠纷处理
- 新增统计缓存系统（Redis + 异步任务），优化梯度返佣计算性能
- 删除冗余的梯度佣金独立 CRUD 接口（合并到分配配置中）
- 归档 3 个已完成的 OpenSpec changes 并同步 8 个新 capabilities 到 main specs

技术细节：
- 数据库迁移：000026_refactor_shop_package_allocation
- 新增 Store：AllocationConfigStore, PriceHistoryStore, CommissionStatsStore
- 新增 Service：BatchAllocationService, BatchPricingService, CommissionStatsService
- 新增异步任务：统计更新、定时同步、周期归档
- 测试覆盖：批量操作集成测试、梯度佣金 CRUD 清理验证

影响：
- API 变更：删除 4 个梯度 CRUD 接口（POST/GET/PUT/DELETE /:id/tiers）
- API 新增：批量分配、批量调价接口
- 数据模型：重构 shop_series_allocation 表结构
- 性能优化：批量操作使用 CreateInBatches，统计使用 Redis 缓存

相关文档：
- openspec/changes/archive/2026-01-28-refactor-shop-package-allocation/
- openspec/specs/agent-available-packages/
- openspec/specs/allocation-config-versioning/
- 等 8 个新 capability specs

internal/service/shop_package_allocation/service.go

@@ -18,6 +18,7 @@ import (
 type Service struct {
 	packageAllocationStore *postgres.ShopPackageAllocationStore
 	seriesAllocationStore  *postgres.ShopSeriesAllocationStore
+	priceHistoryStore      *postgres.ShopPackageAllocationPriceHistoryStore
 	shopStore              *postgres.ShopStore
 	packageStore           *postgres.PackageStore
 }
@@ -25,12 +26,14 @@ type Service struct {
 func New(
 	packageAllocationStore *postgres.ShopPackageAllocationStore,
 	seriesAllocationStore *postgres.ShopSeriesAllocationStore,
+	priceHistoryStore *postgres.ShopPackageAllocationPriceHistoryStore,
 	shopStore *postgres.ShopStore,
 	packageStore *postgres.PackageStore,
 ) *Service {
 	return &Service{
 		packageAllocationStore: packageAllocationStore,
 		seriesAllocationStore:  seriesAllocationStore,
+		priceHistoryStore:      priceHistoryStore,
 		shopStore:              shopStore,
 		packageStore:           packageStore,
 	}
@@ -271,3 +274,76 @@ func (s *Service) buildResponse(ctx context.Context, a *model.ShopPackageAllocat
 		UpdatedAt:           a.UpdatedAt.Format(time.RFC3339),
 	}, nil
 }
+
+func (s *Service) UpdateCostPrice(ctx context.Context, id uint, newCostPrice int64, changeReason string) (*dto.ShopPackageAllocationResponse, error) {
+	currentUserID := middleware.GetUserIDFromContext(ctx)
+	if currentUserID == 0 {
+		return nil, errors.New(errors.CodeUnauthorized, "未授权访问")
+	}
+
+	allocation, err := s.packageAllocationStore.GetByID(ctx, id)
+	if err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "分配记录不存在")
+		}
+		return nil, fmt.Errorf("获取分配记录失败: %w", err)
+	}
+
+	if allocation.CostPrice == newCostPrice {
+		return nil, errors.New(errors.CodeInvalidParam, "新成本价与当前成本价相同")
+	}
+
+	oldCostPrice := allocation.CostPrice
+	now := time.Now()
+
+	priceHistory := &model.ShopPackageAllocationPriceHistory{
+		AllocationID:  allocation.ID,
+		OldCostPrice:  oldCostPrice,
+		NewCostPrice:  newCostPrice,
+		ChangeReason:  changeReason,
+		ChangedBy:     currentUserID,
+		EffectiveFrom: now,
+	}
+	if err := s.priceHistoryStore.Create(ctx, priceHistory); err != nil {
+		return nil, fmt.Errorf("创建价格历史记录失败: %w", err)
+	}
+
+	allocation.CostPrice = newCostPrice
+	allocation.Updater = currentUserID
+	if err := s.packageAllocationStore.Update(ctx, allocation); err != nil {
+		return nil, fmt.Errorf("更新成本价失败: %w", err)
+	}
+
+	shop, _ := s.shopStore.GetByID(ctx, allocation.ShopID)
+	pkg, _ := s.packageStore.GetByID(ctx, allocation.PackageID)
+
+	shopName := ""
+	packageName := ""
+	packageCode := ""
+	if shop != nil {
+		shopName = shop.ShopName
+	}
+	if pkg != nil {
+		packageName = pkg.PackageName
+		packageCode = pkg.PackageCode
+	}
+
+	return s.buildResponse(ctx, allocation, shopName, packageName, packageCode)
+}
+
+func (s *Service) GetPriceHistory(ctx context.Context, allocationID uint) ([]*model.ShopPackageAllocationPriceHistory, error) {
+	_, err := s.packageAllocationStore.GetByID(ctx, allocationID)
+	if err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "分配记录不存在")
+		}
+		return nil, fmt.Errorf("获取分配记录失败: %w", err)
+	}
+
+	history, err := s.priceHistoryStore.ListByAllocation(ctx, allocationID)
+	if err != nil {
+		return nil, fmt.Errorf("获取价格历史失败: %w", err)
+	}
+
+	return history, nil
+}