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）

migrations/000043_simplify_commission_allocation.up.sql

@@ -0,0 +1,61 @@
+-- 简化佣金分配模型：删除 ShopSeriesAllocation 层，使用 ShopPackageAllocation 直接管理
+-- 重构原因：业务模型只需要套餐级别的分配，不需要系列级别的中间层
+
+-- ============================================
+-- 1. 为 ShopPackageAllocation 添加新字段
+-- ============================================
+
+-- 添加 series_id 字段（记录套餐所属系列，便于查询）
+ALTER TABLE tb_shop_package_allocation
+ADD COLUMN IF NOT EXISTS series_id BIGINT DEFAULT 0 NOT NULL;
+
+COMMENT ON COLUMN tb_shop_package_allocation.series_id IS '套餐系列ID（冗余字段，便于查询）';
+
+-- 添加 allocator_shop_id 字段（记录是谁分配的，0表示平台分配）
+ALTER TABLE tb_shop_package_allocation
+ADD COLUMN IF NOT EXISTS allocator_shop_id BIGINT DEFAULT 0 NOT NULL;
+
+COMMENT ON COLUMN tb_shop_package_allocation.allocator_shop_id IS '分配者店铺ID（0表示平台分配）';
+
+-- ============================================
+-- 2. 从现有数据迁移 series_id 和 allocator_shop_id
+-- ============================================
+
+-- 通过 package 表获取 series_id
+UPDATE tb_shop_package_allocation spa
+SET series_id = p.series_id
+FROM tb_package p
+WHERE spa.package_id = p.id AND spa.series_id = 0;
+
+-- 通过 shop_series_allocation 获取 allocator_shop_id
+UPDATE tb_shop_package_allocation spa
+SET allocator_shop_id = ssa.allocator_shop_id
+FROM tb_shop_series_allocation ssa
+WHERE spa.allocation_id = ssa.id AND spa.allocator_shop_id = 0;
+
+-- ============================================
+-- 3. 删除废弃的 allocation_id 字段
+-- ============================================
+
+ALTER TABLE tb_shop_package_allocation
+DROP COLUMN IF EXISTS allocation_id;
+
+-- ============================================
+-- 4. 添加索引优化查询性能
+-- ============================================
+
+CREATE INDEX IF NOT EXISTS idx_shop_package_allocation_series_id 
+ON tb_shop_package_allocation(series_id);
+
+CREATE INDEX IF NOT EXISTS idx_shop_package_allocation_allocator_shop_id 
+ON tb_shop_package_allocation(allocator_shop_id);
+
+-- ============================================
+-- 5. 删除废弃的表
+-- ============================================
+
+-- 删除系列分配配置表
+DROP TABLE IF EXISTS tb_shop_series_allocation_config;
+
+-- 删除系列分配表
+DROP TABLE IF EXISTS tb_shop_series_allocation;