fix(onboarding): skip org name prompt for vendor-created admins

Vendor-created tenant admins already have an org membership. When they
land on /onboarding (first login, token lacks org claims), detect the
existing tenant via /api/me and trigger a re-auth to pick up org
membership instead of showing the org name form.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/OnboardingPage.tsx

@@ -1,8 +1,9 @@
 import { useState, useEffect, useRef } from 'react';
 import { useLogto } from '@logto/react';
-import { Card, Input, Button, FormField, Alert } from '@cameleer/design-system';
+import { Card, Input, Button, FormField, Alert, Spinner } from '@cameleer/design-system';
 import cameleerLogo from '@cameleer/design-system/assets/cameleer-logo.svg';
 import { api, errorMessage } from '../api/client';
+import { useMe } from '../api/hooks';
 import { toSlug } from '../utils/slug';
 import styles from './OnboardingPage.module.css';
 
@@ -15,6 +16,7 @@ interface TenantResponse {
 
 export function OnboardingPage() {
   const { signIn } = useLogto();
+  const { data: me, isLoading: meLoading } = useMe();
   const [name, setName] = useState('');
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
@@ -24,6 +26,14 @@ export function OnboardingPage() {
 
   const slug = toSlug(name);
 
+  // Vendor-created admins already have an org — skip onboarding and re-auth
+  // to pick up org membership in the token
+  useEffect(() => {
+    if (!meLoading && me && me.tenants.length > 0) {
+      signIn(`${window.location.origin}/platform/callback`);
+    }
+  }, [me, meLoading, signIn]);
+
   useEffect(() => {
     setSlugAvailable(null);
     if (!slug) return;
@@ -66,6 +76,17 @@ export function OnboardingPage() {
     }
   }
 
+  // Show spinner while checking org membership or redirecting
+  if (meLoading || (me && me.tenants.length > 0)) {
+    return (
+      <div className={styles.page}>
+        <div style={{ display: 'flex', justifyContent: 'center', padding: 64 }}>
+          <Spinner />
+        </div>
+      </div>
+    );
+  }
+
   return (
     <div className={styles.page}>
       <div className={styles.wrapper}>