refactor: update registry type from 'docker-hub' to 'oci' across seed data (#325)

Updates the registry type for all Docker Hub packages in the seed data
from `docker-hub` to `oci` to align with the standardized OCI registry
format. This change affects the `registry_type` field and simplifies the
`identifier` field by removing the full Docker Hub URL prefix.

Changes:
- Updated `registry_type` from `docker-hub` to `oci` for all Docker
packages
- Simplified `identifier` field to use just the repository name/path
instead of full URLs
- Maintained `registry_base_url` as `https://docker.io` for all entries

This refactoring improves consistency and aligns with OCI standards
while maintaining backward compatibility through the registry base URL.

internal/validators/validators.go

@@ -189,8 +189,7 @@ func validatePackage(pkg *model.Package) error {
 		return nil
 	}
 
-	// For registry-based packages, no special validation needed
-	// Registry types like "npm", "pypi", "docker-hub", "nuget" are all valid
+	// For other registry-based packages, no special validation needed
 	return nil
 }