fix: 添加V14迁移为order_items表增加length,width,area字段

src/main/resources/db/migration/V14__add_order_item_size_fields.sql

@@ -0,0 +1,7 @@
+-- 添加订单明细长度、宽度、面积字段
+ALTER TABLE order_items ADD COLUMN length DECIMAL(10,2);
+COMMENT ON COLUMN order_items.length IS '长度(mm)';
+ALTER TABLE order_items ADD COLUMN width DECIMAL(10,2);
+COMMENT ON COLUMN order_items.width IS '宽度(mm)';
+ALTER TABLE order_items ADD COLUMN area DECIMAL(10,4);
+COMMENT ON COLUMN order_items.area IS '面积(m²)';