refactor: 一次性佣金配置从套餐级别提升到系列级别

主要变更:
- 新增 tb_shop_series_allocation 表，存储系列级别的一次性佣金配置
- ShopPackageAllocation 移除 one_time_commission_amount 字段
- PackageSeries 新增 enable_one_time_commission 字段控制是否启用一次性佣金
- 新增 /api/admin/shop-series-allocations CRUD 接口
- 佣金计算逻辑改为从 ShopSeriesAllocation 获取一次性佣金金额
- 删除废弃的 ShopSeriesOneTimeCommissionTier 模型
- OpenAPI Tag '系列分配' 和 '单套餐分配' 合并为 '套餐分配'

迁移脚本:
- 000042: 重构佣金套餐模型
- 000043: 简化佣金分配
- 000044: 一次性佣金分配重构
- 000045: PackageSeries 添加 enable_one_time_commission 字段

测试:
- 新增验收测试 (shop_series_allocation, commission_calculation)
- 新增流程测试 (one_time_commission_chain)
- 删除过时的单元测试（已被验收测试覆盖）

internal/bootstrap/stores.go

@@ -33,8 +33,6 @@ type stores struct {
 	PackageSeries                     *postgres.PackageSeriesStore
 	Package                           *postgres.PackageStore
 	ShopSeriesAllocation              *postgres.ShopSeriesAllocationStore
-	ShopSeriesOneTimeCommissionTier   *postgres.ShopSeriesOneTimeCommissionTierStore
-	ShopSeriesAllocationConfig        *postgres.ShopSeriesAllocationConfigStore
 	ShopPackageAllocation             *postgres.ShopPackageAllocationStore
 	ShopPackageAllocationPriceHistory *postgres.ShopPackageAllocationPriceHistoryStore
 	ShopSeriesCommissionStats         *postgres.ShopSeriesCommissionStatsStore
@@ -73,8 +71,6 @@ func initStores(deps *Dependencies) *stores {
 		PackageSeries:                     postgres.NewPackageSeriesStore(deps.DB),
 		Package:                           postgres.NewPackageStore(deps.DB),
 		ShopSeriesAllocation:              postgres.NewShopSeriesAllocationStore(deps.DB),
-		ShopSeriesOneTimeCommissionTier:   postgres.NewShopSeriesOneTimeCommissionTierStore(deps.DB),
-		ShopSeriesAllocationConfig:        postgres.NewShopSeriesAllocationConfigStore(deps.DB),
 		ShopPackageAllocation:             postgres.NewShopPackageAllocationStore(deps.DB),
 		ShopPackageAllocationPriceHistory: postgres.NewShopPackageAllocationPriceHistoryStore(deps.DB),
 		ShopSeriesCommissionStats:         postgres.NewShopSeriesCommissionStatsStore(deps.DB),