fix: Set org.opencontainers.image.created annotation on ModelKit manifests

Add the standard OCI annotation `org.opencontainers.image.created` with the current time in RFC 3339 format to ModelKit manifests during the pack operation, alongside the existing `ml.kitops.modelkit.cli-version` annotation.

Fixes #1138

Signed-off-by: itniuma <itniuma@proton.me>

Author: itniuma2026

pkg/lib/filesystem/local-storage.go

@@ -23,6 +23,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"time"
 
 	"github.com/kitops-ml/kitops/pkg/artifact"
 	"github.com/kitops-ml/kitops/pkg/lib/constants"
@@ -64,6 +65,11 @@ func SaveModel(ctx context.Context, localRepo local.LocalRepo, kitfile *artifact
 		return nil, fmt.Errorf("error creating manifest: %w", err)
 	}
 
+	if manifest.Annotations == nil {
+		manifest.Annotations = map[string]string{}
+	}
+	manifest.Annotations[ocispec.AnnotationCreated] = time.Now().UTC().Format(time.RFC3339)
+
 	// If not storing a Kitfile, save the Kitfile to an annotation since it will be lost otherwise
 	if opts.ModelFormat == mediatype.ModelPackFormat {
 		kitfileBytes, err := kitfile.MarshalToJSON()