Add XML documentation across gateway, worker, and .NET client

src/MxGateway.Server/Dashboard/IDashboardAuthenticator.cs

@@ -1,7 +1,15 @@
 namespace MxGateway.Server.Dashboard;
 
+/// <summary>
+/// Authenticates dashboard access with API keys.
+/// </summary>
 public interface IDashboardAuthenticator
 {
+    /// <summary>
+    /// Authenticates the dashboard session with an API key.
+    /// </summary>
+    /// <param name="apiKey">The API key to authenticate.</param>
+    /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>
     Task<DashboardAuthenticationResult> AuthenticateAsync(
         string? apiKey,
         CancellationToken cancellationToken);