allow only registered publishers to set up local credentials; fix menu; fix signin UI

pages/auth/signin.tsx

@@ -47,13 +47,14 @@ export default function SignIn({ csrfToken }) {
                 <div className="signin">
                     <div className="min-h-screen flex flex-col items-center justify-center">
                         {/* SSO Providers */}
-                        <div className="space-y-4 w-full px-4">
+                        <div className="mt-8 w-full max-w-xs px-4">
                             <button onClick={() => signIn('google', { callbackUrl: '/' })}
                                 className="flex items-center justify-center w-full py-2 px-4 border border-gray-300 rounded shadow-sm text-sm text-gray-700 bg-white hover:bg-gray-50">
                                 <img loading="lazy" height="24" width="24" alt="Google logo"
                                     src="https://authjs.dev/img/providers/google.svg" className="mr-2" />
                                 Влез чрез Google
                             </button>
+
                             {/* Add more buttons for other SSO providers here in similar style */}
                         </div>