feat: add HTTP Management API, migrate CLI from Akka ClusterClient to HTTP

Replace the CLI's Akka.NET ClusterClient transport with a simple HTTP client
targeting a new POST /management endpoint on the Central Host. The endpoint
handles Basic Auth, LDAP authentication, role resolution, and ManagementActor
dispatch in a single round-trip — eliminating the CLI's Akka, LDAP, and
Security dependencies.

Also fixes DCL ReSubscribeAll losing subscriptions on repeated reconnect by
deriving the tag list from _subscriptionsByInstance instead of _subscriptionIds.

tests/ScadaLink.Commons.Tests/Messages/MessageConventionTests.cs

@@ -13,6 +13,8 @@ public class MessageConventionTests
                         && t.Namespace.Contains(".Messages.")
                         && !t.IsEnum
                         && !t.IsInterface
+                        && !(t.IsAbstract && t.IsSealed) // exclude static classes (utilities)
+                        && !t.Name.StartsWith("<") // exclude compiler-generated types
                         && (t.IsClass || (t.IsValueType && !t.IsPrimitive)));
 
     [Fact]