Browse Skill Catalog

List the skills published in the public data-engineering-skills repo.

Declared ahead of /{public_id} so that "catalog" is routed here rather than being read as a skill identifier.

Each entry carries imported_public_id when the caller already imported it, so the Browse list can link to their copy instead of offering a second import. That is matched on the upstream path, not the name, so it survives the user renaming their copy.