feat: add per-client trace mode flag with dynamic parser logger

src/NATS.Server/Protocol/NatsParser.cs

@@ -36,7 +36,8 @@ public sealed class NatsParser
 {
     private static readonly byte[] CrLfBytes = "\r\n"u8.ToArray();
     private readonly int _maxPayload;
-    private readonly ILogger? _logger;
+    private ILogger? _logger;
+    public ILogger? Logger { set => _logger = value; }
 
     // State for split-packet payload reading
     private bool _awaitingPayload;