fix: add error callback for UNIX socket connection errors in main.go

- Configure ErrorCallback on output builder to log socket connection failures
- Errors now visible via appLogger.Error when socket connection fails
- Helps diagnose missing socket or permission issues

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

cmd/ja4sentinel/main.go

@@ -115,7 +115,15 @@ func main() {
 	captureEngine := capture.New()
 	parser := tlsparse.NewParserWithTimeout(time.Duration(appConfig.Core.FlowTimeoutSec) * time.Second)
 	fingerprintEngine := fingerprint.NewEngine()
-	outputBuilder := output.NewBuilder()
+	
+	// Create output builder with error callback for socket connection errors
+	outputBuilder := output.NewBuilder().WithErrorCallback(func(socketPath string, err error, attempt int) {
+		appLogger.Error("output", "UNIX socket connection failed", map[string]string{
+			"socket_path": socketPath,
+			"error":       err.Error(),
+			"attempt":     fmt.Sprintf("%d", attempt),
+		})
+	})
 
 	outputWriter, err := outputBuilder.NewFromConfig(appConfig)
 	if err != nil {