fix(dcl): harden endpoint host-rewrite — IPv6 brackets + portless URLs

Code review of a1abbff7 found two edge cases: a discovery/advertised URL with no
explicit port emitted a malformed ':-1' (opc.tcp has no Uri default port), and an
IPv6 literal host could lose/double its brackets. Omit the port when neither URL
carries one; bracket an IPv6 host only when missing. +4 tests (12 total).

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs

@@ -191,11 +191,21 @@ public class RealOpcUaClient : IOpcUaClient
             && advertised.Port == reachable.Port)
             return;
 
+        // An IPv6 literal must keep its brackets, or the reconstructed authority (`::1:4840`) is
+        // ambiguous and unparseable. Uri.Host may or may not include them depending on the scheme,
+        // so bracket only when missing (never double-wrap).
+        var host = reachable.Host;
+        if (reachable.HostNameType == UriHostNameType.IPv6 && !host.StartsWith('['))
+            host = $"[{host}]";
+        // opc.tcp has no default port known to Uri, so Uri.Port is -1 when the text omits one.
+        // Prefer the reachable URL's port, fall back to the advertised one, and emit no ":port"
+        // at all when neither carries one (rather than a malformed ":-1").
         var port = reachable.Port >= 0 ? reachable.Port : advertised.Port;
+        var authority = port >= 0 ? $"{host}:{port}" : host;
         // Authority-only advertisements parse to AbsolutePath "/" — drop it so we don't append a
         // spurious trailing slash the server never advertised.
         var path = advertised.AbsolutePath == "/" ? string.Empty : advertised.AbsolutePath;
-        endpoint.EndpointUrl = $"{advertised.Scheme}://{reachable.Host}:{port}{path}";
+        endpoint.EndpointUrl = $"{advertised.Scheme}://{authority}{path}";
     }
 
     /// <summary>