feat: 足额免配送费

yshop-drink-boot3/sql/upgrade_free_delivery_amount.sql

@@ -0,0 +1,3 @@
+ALTER TABLE `yshop_store_shop`
+  ADD COLUMN `free_delivery_amount` decimal(10,2) NOT NULL DEFAULT '0.00'
+  COMMENT '满额免配送费门槛，0表示不启用' AFTER `delivery_rules`;