test 3/4: single .NET sample README

Author: ksroda-sa

samples/dotnet/login-auth-code/README.md

@@ -2,6 +2,8 @@
 
 Minimal ASP.NET Core 10 Minimal-APIs app demonstrating server-side OIDC login using `Microsoft.AspNetCore.Authentication.OpenIdConnect`. The server holds the client secret and manages the session via an encrypted auth cookie.
 
+> Looking for the token-refresh variant? See [`samples/dotnet/token-refresh/`](../token-refresh/).
+
 ## Prerequisites
 
 - .NET 10 SDK installed (`dotnet --version` → 10.x)