feat: add project setup for monitoring and TLS — csproj, config options, ServerInfo TLS fields

Add FrameworkReference to Microsoft.AspNetCore.App to enable Kestrel
Minimal APIs for the monitoring HTTP server. Remove the now-redundant
Microsoft.Extensions.Logging.Abstractions PackageReference (it is
included transitively via the framework reference).

Add monitoring config properties (MonitorPort, MonitorHost,
MonitorBasePath, MonitorHttpsPort) and TLS config properties (TlsCert,
TlsKey, TlsCaCert, TlsVerify, TlsHandshakeFirst, etc.) to NatsOptions.

Add TlsRequired, TlsVerify, and TlsAvailable fields to ServerInfo so
the server can advertise TLS capability in the INFO protocol message.

src/NATS.Server/Protocol/NatsProtocol.cs

@@ -61,6 +61,18 @@ public sealed class ServerInfo
     [JsonPropertyName("client_ip")]
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     public string? ClientIp { get; set; }
+
+    [JsonPropertyName("tls_required")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+    public bool TlsRequired { get; set; }
+
+    [JsonPropertyName("tls_verify")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+    public bool TlsVerify { get; set; }
+
+    [JsonPropertyName("tls_available")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+    public bool TlsAvailable { get; set; }
 }
 
 public sealed class ClientOptions