fix: stop pulling node:dns into client bundle via OAuth discovery

app/api/auth/sso/start/route.ts

@@ -5,6 +5,7 @@ import { encryptPayload } from '@/lib/auth/crypto';
 import { generateCodeVerifierServer, generateCodeChallengeServer, generateStateServer } from '@/lib/oauth/pkce-server';
 import { getRequiredConfig } from '@/lib/oauth/token-exchange';
 import { discoverOAuth } from '@/lib/oauth/discovery';
+import { isPublicHttpUrl } from '@/lib/security/url-guard';
 import { getOauthScopes } from '@/lib/oauth/tokens';
 import { getCookieOptions } from '@/lib/oauth/cookie-config';
 import { hasSessionSecret } from '@/lib/auth/session-secret';
@@ -39,7 +40,7 @@ export async function POST(request: NextRequest) {
     }
 
     const { clientId, discoveryUrl } = getRequiredConfig(serverId);
-    const metadata = await discoverOAuth(discoveryUrl);
+    const metadata = await discoverOAuth(discoveryUrl, { validateEndpoint: isPublicHttpUrl });
 
     if (!metadata?.authorization_endpoint) {
       return NextResponse.json({ error: 'OAuth discovery failed' }, { status: 502 });

app/api/auth/totp-token-exchange/route.ts

@@ -54,7 +54,7 @@ async function tryTokenRequest(
 
 async function findTokenEndpoint(serverUrl: string): Promise<string | null> {
   // 1. Try OAuth discovery
-  const metadata = await discoverOAuth(serverUrl);
+  const metadata = await discoverOAuth(serverUrl, { validateEndpoint: isPublicHttpUrl });
   if (metadata?.token_endpoint) return metadata.token_endpoint;
 
   // 2. Try common Stalwart token endpoint paths directly