feat: add NATS NKey authentication support

Allow authentication to NATS using NKey seed files as an alternative to
credentials files. NKeys use Ed25519 key pairs for authentication.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

main.go

@@ -15,7 +15,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
-const version = "0.3.0"
+const version = "0.4.0"
 
 func main() {
 	cfg, err := config.Parse()
@@ -40,6 +40,7 @@ func main() {
 			NATSURL:             cfg.FlakeNATSURL,
 			NATSSubject:         cfg.FlakeNATSSubject,
 			NATSCredentialsFile: cfg.FlakeNATSCredentialsFile,
+			NATSNkeySeedFile:    cfg.FlakeNATSNkeySeedFile,
 		})
 		if err != nil {
 			slog.Error("Failed to create flake collector", "error", err)