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.

src/ScadaLink.Host/Program.cs

@@ -129,6 +129,7 @@ try
         app.MapStaticAssets();
         app.MapCentralUI<ScadaLink.Host.Components.App>();
         app.MapInboundAPI();
+        app.MapManagementAPI();
 
         // Compile and register all Inbound API method scripts at startup
         using (var scope = app.Services.CreateScope())