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.DataConnectionLayer/Actors/DataConnectionActor.cs

@@ -483,11 +483,18 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
 
     private void ReSubscribeAll()
     {
-        _log.Info("[{0}] Re-subscribing {1} tags after reconnect", _connectionName, _subscriptionIds.Count);
+        // Derive tag list from _subscriptionsByInstance (durable source of truth),
+        // not _subscriptionIds which gets cleared and is only repopulated on success.
+        var allTags = _subscriptionsByInstance.Values
+            .SelectMany(tags => tags)
+            .Distinct()
+            .ToList();
+
+        _log.Info("[{0}] Re-subscribing {1} tags after reconnect", _connectionName, allTags.Count);
 
         var self = Self;
-        var allTags = _subscriptionIds.Keys.ToList();
         _subscriptionIds.Clear();
+        _unresolvedTags.Clear();
         _resolvedTags = 0;
 
         foreach (var tagPath in allTags)
@@ -535,6 +542,16 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
     {
         _log.Debug("[{0}] Tag resolution still failing for {1}: {2}",
             _connectionName, msg.TagPath, msg.Error);
+
+        // Track as unresolved so periodic retry picks it up
+        if (_unresolvedTags.Add(msg.TagPath))
+        {
+            Timers.StartPeriodicTimer(
+                "tag-resolution-retry",
+                new RetryTagResolution(),
+                _options.TagResolutionRetryInterval,
+                _options.TagResolutionRetryInterval);
+        }
     }
 
     private void HandleTagValueReceived(TagValueReceived msg)