Introduce tree view and artifact metadata visibility in Virtual Registries

🔥 Problem

When viewing artifacts within an upstream, users find it difficult to understand how related files (for example, JAR and POM in Maven) connect to each other. The current flat view makes it hard to identify which files belong together or represent different variants of the same artifact.

💡 Proposal

• Add a tree view within each upstream to show the relationship between artifacts that share a common coordinate or group.
• Surface artifact metadata (version, type, checksum, origin, etc.) directly in the list to help users interpret structure and relationships without guessing from filenames.