feat: add filename to error message when yaml file is invalid

Before:
FATA <internal/validate.go:84> unable to validate recipe: yaml: line 3: did not find expected key

After:
FATA <internal/validate.go:84> unable to validate recipe: <redacted>/recipes/monitoring-ng/compose.grafana-oidc.yml: yaml: line 3: did not find expected key

pkg/upstream/stack/loader.go

@@ -138,7 +138,7 @@ func loadConfigFile(filename string) (*composetypes.ConfigFile, error) {
 
 	config, err := loader.ParseYAML(bytes)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("%s: %s", filename, err)
 	}
 
 	return &composetypes.ConfigFile{