实现支付商户池与微信授权配置

新增收款商户、商户池轮询、微信授权配置独立管理；三类新支付
（C端套餐购买、C端资产钱包充值、代理在线预存款充值）无条件
经商户池选择并冻结路由，无旧综合配置回退。merchant_id 为空
历史支付继续按 payment_config_id 双读。凭证版本化加载与
ID+版本缓存保证轮换一致性。删除商户池新支付创建开关及全部
引用。

migrations/000210_add_payment_merchant_pools.down.sql

@@ -0,0 +1,32 @@
+-- 回滚商户池支付路由 Schema。
+-- 任一新路由支付、成功累计或新配置事实存在时均禁止破坏性回滚。
+DO $$
+BEGIN
+    IF EXISTS (SELECT 1 FROM tb_payment WHERE merchant_id IS NOT NULL OR merchant_pool_id IS NOT NULL)
+       OR EXISTS (SELECT 1 FROM tb_payment_merchant_routing_success)
+       OR EXISTS (SELECT 1 FROM tb_payment_merchant)
+       OR EXISTS (SELECT 1 FROM tb_payment_merchant_pool)
+       OR EXISTS (SELECT 1 FROM tb_payment_merchant_pool_member)
+       OR EXISTS (SELECT 1 FROM tb_wechat_authorization) THEN
+        RAISE EXCEPTION '存在商户池支付路由业务事实，禁止回滚商户池支付路由迁移';
+    END IF;
+END $$;
+
+DROP INDEX IF EXISTS idx_payment_merchant_pool_route;
+DROP INDEX IF EXISTS idx_payment_merchant_route;
+
+ALTER TABLE tb_payment
+    DROP COLUMN IF EXISTS routing_epoch,
+    DROP COLUMN IF EXISTS routing_strategy_snapshot,
+    DROP COLUMN IF EXISTS merchant_pool_name_snapshot,
+    DROP COLUMN IF EXISTS merchant_provider_type_snapshot,
+    DROP COLUMN IF EXISTS merchant_payment_method_snapshot,
+    DROP COLUMN IF EXISTS merchant_name_snapshot,
+    DROP COLUMN IF EXISTS merchant_pool_id,
+    DROP COLUMN IF EXISTS merchant_id;
+
+DROP TABLE IF EXISTS tb_payment_merchant_routing_success;
+DROP TABLE IF EXISTS tb_wechat_authorization;
+DROP TABLE IF EXISTS tb_payment_merchant_pool_member;
+DROP TABLE IF EXISTS tb_payment_merchant_pool;
+DROP TABLE IF EXISTS tb_payment_merchant;