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）

tests/integration/package_test.go

@@ -416,7 +416,6 @@ func TestPackageAPI_Get(t *testing.T) {
 		PackageName:    "测试套餐",
 		PackageType:    "formal",
 		DurationMonths: 12,
-		Price:          99900,
 		Status:         constants.StatusEnabled,
 		ShelfStatus:    2,
 		BaseModel: model.BaseModel{
@@ -452,7 +451,6 @@ func TestPackageAPI_List(t *testing.T) {
 			PackageName:    "列表测试套餐1",
 			PackageType:    "formal",
 			DurationMonths: 12,
-			Price:          99900,
 			Status:         constants.StatusEnabled,
 			ShelfStatus:    1,
 			BaseModel:      model.BaseModel{Creator: 1},
@@ -462,7 +460,6 @@ func TestPackageAPI_List(t *testing.T) {
 			PackageName:    "列表测试套餐2",
 			PackageType:    "addon",
 			DurationMonths: 1,
-			Price:          9990,
 			Status:         constants.StatusEnabled,
 			ShelfStatus:    2,
 			BaseModel:      model.BaseModel{Creator: 1},
@@ -495,7 +492,6 @@ func TestPackageAPI_Update(t *testing.T) {
 		PackageName:    "原始套餐名称",
 		PackageType:    "formal",
 		DurationMonths: 12,
-		Price:          99900,
 		Status:         constants.StatusEnabled,
 		ShelfStatus:    2,
 		BaseModel: model.BaseModel{
@@ -538,7 +534,6 @@ func TestPackageAPI_Delete(t *testing.T) {
 		PackageName:    "测试套餐",
 		PackageType:    "formal",
 		DurationMonths: 12,
-		Price:          99900,
 		Status:         constants.StatusEnabled,
 		ShelfStatus:    2,
 		BaseModel: model.BaseModel{