fix: resolve CLI serialization failures and add README

Two Akka.NET deserialization bugs prevented CLI commands from reaching ManagementActor: IReadOnlyList<string> in AuthenticatedUser serialized as a compiler-generated internal type unknown to the server, and ManagementSuccess.Data carried server-side assembly types the CLI couldn't resolve on receipt. Fixed by using string[] for roles and pre-serializing response data to JSON in ManagementActor before sending. Adds full CLI reference documentation covering all 10 command groups.

src/ScadaLink.ManagementService/ManagementActor.cs

@@ -1,5 +1,6 @@
 using System.Security.Cryptography;
 using Akka.Actor;
+using Newtonsoft.Json;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using ScadaLink.Commons.Entities.ExternalSystems;
@@ -56,7 +57,8 @@ public class ManagementActor : ReceiveActor
             try
             {
                 var result = await DispatchCommand(scope.ServiceProvider, envelope.Command, user.Username);
-                sender.Tell(new ManagementSuccess(correlationId, result));
+                var json = JsonConvert.SerializeObject(result, Formatting.None);
+                sender.Tell(new ManagementSuccess(correlationId, json));
             }
             catch (Exception ex)
             {