fix(auth): transfer WeChat id on merge; stop false phone prompts

Merge used to drop wxOpenId so OAuth created a new guest without phone every time. Now migrate WeChat identity, recover legacy merged openIds, return accountMerged and force page reload, and only soft-prompt when phone is truly unbound.

apps/mini-user/src/pages/login/index.tsx

@@ -10,7 +10,7 @@ import {
 import PageShell from '../../components/PageShell';
 import WechatLoginButton from '../../components/WechatLoginButton';
 import { BRAND_LOGO_WIDE_URL } from '@dukang/shared-types';
-import { finishLoginNavigate } from '../../lib/auth-nav';
+import { finishLoginNavigate, forceReloadAfterAccountMerge } from '../../lib/auth-nav';
 import {
   bindWechatForUser,
   loginWithWechat,
@@ -126,6 +126,10 @@ export default function LoginPage() {
         .catch(() => {});
     }
     toast(successToast, 'success');
+    if (data.accountMerged) {
+      forceReloadAfterAccountMerge(returnTo);
+      return;
+    }
     finishLoginNavigate(returnTo);
   }