feat: record who created join codes and who added each node [CI]

backend/fleet/src/Fleet.Server.Abstractions/NodeRecords.cs

@@ -33,7 +33,8 @@ public sealed record NewNode(
     string? NodeVersion,
     long NowMs,
     string Kind = "",
-    byte[]? TlsPublicKey = null);
+    byte[]? TlsPublicKey = null,
+    string? AddedBy = null);
 
 public sealed record JoinTokenRecord(
     string Id,
@@ -46,6 +47,7 @@ public sealed record JoinTokenRecord(
     long ExpiresAtMs,
     long? RevokedAtMs,
     long CreatedAtMs,
-    string Kind = "");
+    string Kind = "",
+    string? CreatedBy = null);
 
 public sealed record Presence(bool Online, long AtMs, string? NodeVersion, IReadOnlyList<string> Capabilities, string? HelloMetaJson);