resolve ABB downloads end to end

[sgerner]

Stacked on #53. This PR wires ABB detail URLs through the download flow and routes audiobook torrents to the audiobook category.

What changed:

• Include abb_url in the browser payload so ABB results can be downloaded from the UI.
• Resolve ABB detail-page URLs into magnets before adding them to qBittorrent.
• Infer audiobook media type for audiobook sources so the torrent lands in the audiobook save path.
• Reuse the same resolution path from request-approval downloads.
• Add regression coverage for ABB URL resolution and the direct-URL fast path.

Validation:

• go test ./internal/api -run 'TestQueryBoundedInt|TestResolveTorrentURL'

Review note:

• This depends on parse ABB info hash from detail rows #53 because ABB detail-page parsing was fixed separately to keep the review focused.

[JeremiahM37]

Please solve merge conflicts