fix: redirect to home page after login/register instead of /trees

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/LoginPage.tsx

@@ -14,7 +14,7 @@ export function LoginPage() {
   const [password, setPassword] = useState('')
   const [localError, setLocalError] = useState('')
 
-  const from = (location.state as { from?: { pathname: string } })?.from?.pathname || '/trees'
+  const from = (location.state as { from?: { pathname: string } })?.from?.pathname || '/'
 
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault()