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.down.sql

@@ -0,0 +1,68 @@
+-- 回滚：恢复 ShopSeriesAllocation 层
+
+-- ============================================
+-- 1. 重建 ShopSeriesAllocation 表
+-- ============================================
+
+CREATE TABLE IF NOT EXISTS tb_shop_series_allocation (
+    id BIGSERIAL PRIMARY KEY,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW(),
+    deleted_at TIMESTAMPTZ,
+    creator BIGINT NOT NULL DEFAULT 0,
+    updater BIGINT NOT NULL DEFAULT 0,
+    shop_id BIGINT NOT NULL,
+    series_id BIGINT NOT NULL,
+    allocator_shop_id BIGINT NOT NULL DEFAULT 0,
+    cost_price_markup BIGINT NOT NULL DEFAULT 0,
+    one_time_commission_amount BIGINT NOT NULL DEFAULT 0,
+    status INTEGER NOT NULL DEFAULT 1
+);
+
+COMMENT ON TABLE tb_shop_series_allocation IS '店铺系列分配表';
+COMMENT ON COLUMN tb_shop_series_allocation.shop_id IS '被分配店铺ID';
+COMMENT ON COLUMN tb_shop_series_allocation.series_id IS '套餐系列ID';
+COMMENT ON COLUMN tb_shop_series_allocation.allocator_shop_id IS '分配者店铺ID（0表示平台分配）';
+COMMENT ON COLUMN tb_shop_series_allocation.cost_price_markup IS '成本价加价（分）';
+COMMENT ON COLUMN tb_shop_series_allocation.one_time_commission_amount IS '一次性佣金金额（分）';
+
+CREATE INDEX IF NOT EXISTS idx_shop_series_allocation_shop_id ON tb_shop_series_allocation(shop_id);
+CREATE INDEX IF NOT EXISTS idx_shop_series_allocation_series_id ON tb_shop_series_allocation(series_id);
+
+-- ============================================
+-- 2. 重建 ShopSeriesAllocationConfig 表
+-- ============================================
+
+CREATE TABLE IF NOT EXISTS tb_shop_series_allocation_config (
+    id BIGSERIAL PRIMARY KEY,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW(),
+    deleted_at TIMESTAMPTZ,
+    creator BIGINT NOT NULL DEFAULT 0,
+    updater BIGINT NOT NULL DEFAULT 0,
+    allocation_id BIGINT NOT NULL,
+    config_type VARCHAR(50) NOT NULL,
+    config_value JSONB
+);
+
+COMMENT ON TABLE tb_shop_series_allocation_config IS '店铺系列分配配置表';
+
+-- ============================================
+-- 3. 恢复 allocation_id 字段
+-- ============================================
+
+ALTER TABLE tb_shop_package_allocation
+ADD COLUMN IF NOT EXISTS allocation_id BIGINT NOT NULL DEFAULT 0;
+
+-- ============================================
+-- 4. 删除新增的字段
+-- ============================================
+
+DROP INDEX IF EXISTS idx_shop_package_allocation_series_id;
+DROP INDEX IF EXISTS idx_shop_package_allocation_allocator_shop_id;
+
+ALTER TABLE tb_shop_package_allocation
+DROP COLUMN IF EXISTS series_id;
+
+ALTER TABLE tb_shop_package_allocation
+DROP COLUMN IF EXISTS allocator_shop_id;