Fixed
- App cache growing to gigabytes. Torrent downloads are staged in the app cache and were
only removed after a successful copy: stopping or failing a download left the partial file
behind for the rest of the session, and every rescan wrote a few random pieces while the
metadata was being fetched. Torrents are now removed together with their files when stopped,
failed or timed out, and metadata is fetched in upload mode (no pieces requested).