feat(db): add sys_user wx_openid columns for mini phone login.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/sql/migrations/2026-09-18-sys-user-wx-openid.sql

@@ -0,0 +1,7 @@
+-- 山峡小程序手机号快捷登录：绑定微信 openid
+ALTER TABLE `sys_user`
+  ADD COLUMN `wx_openid` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '微信小程序 openid' AFTER `avatar`,
+  ADD COLUMN `wx_unionid` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL COMMENT '微信 unionid' AFTER `wx_openid`;
+
+ALTER TABLE `sys_user`
+  ADD UNIQUE KEY `uk_sys_user_wx_openid` (`wx_openid`);