fix: resolve golangci-lint errcheck warnings

- Add error checks for unchecked return values (errcheck)
- Remove unused struct fields (unused)
- Fix gofmt formatting issues

main.go

@@ -151,7 +151,7 @@ func submitArgo(ctx context.Context, client *http.Client, host, namespace, templ
 	if err != nil {
 		return "", fmt.Errorf("argo request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	respBody, _ := io.ReadAll(resp.Body)
 
 	if resp.StatusCode >= 400 {
@@ -196,7 +196,7 @@ func submitKubeflow(ctx context.Context, client *http.Client, host, pipelineID s
 	if err != nil {
 		return "", fmt.Errorf("kubeflow request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	respBody, _ := io.ReadAll(resp.Body)
 
 	if resp.StatusCode >= 400 {