feat: parse cluster and jetstream config blocks

src/NATS.Server/NatsOptions.cs

@@ -1,5 +1,6 @@
 using System.Security.Authentication;
 using NATS.Server.Auth;
+using NATS.Server.Configuration;
 using NATS.Server.Tls;
 
 namespace NATS.Server;
@@ -115,6 +116,12 @@ public sealed class NatsOptions
     // Subject mapping / transforms (source pattern -> destination template)
     public Dictionary<string, string>? SubjectMappings { get; set; }
 
+    // Cluster and JetStream settings
+    public ClusterOptions? Cluster { get; set; }
+    public GatewayOptions? Gateway { get; set; }
+    public LeafNodeOptions? LeafNode { get; set; }
+    public JetStreamOptions? JetStream { get; set; }
+
     public bool HasTls => TlsCert != null && TlsKey != null;
 
     // WebSocket