Cleaner detail page layout with separate metadata and body cards

Forage item detail pages now separate metadata and body into two distinct cards. The top card shows metadata, including source, requester, updated date, and domain badges. The rendered item body appears in its own Details card below. This makes the detail page easier to scan, especially for long GitHub issues with Markdown content. The change applies to all forage item types: manual items, GitHub issues, and Grafana alerts. No data, route, feed, or configuration changes are included.