feat(web): add one-click VLC action to single-file torrent cards

[SHAREN]

Why

For a movie torrent with one playable video file, TorrServer already knows exactly which file the user wants. Opening VLC currently requires opening Info, finding the file, and pressing VLC there.

This adds the same action directly to the torrent card, so the common case becomes one click.

What changed

• Adds a separate Show VLC button on torrent cards preference.
• The preference is off by default.
• Shows a VLC button on the main card only when:
  • VLC is enabled in the existing player settings;
  • the new card-button preference is also enabled;
  • the torrent contains exactly one playable video file.
• Applies player-setting changes immediately without requiring a page reload.
• Uses the same TorrServer stream URL and vlc:// protocol already used in the file details view.
• Builds an absolute stream URL, so it also works when the Web UI is opened through another hostname or reverse proxy.

What did not change

• No server API changes.
• Multi-file torrents still require choosing a file in Info.
• Existing Play, Playlist, and Info actions remain unchanged.
• Existing users do not see the new button until they explicitly enable the new preference.
• Users who have VLC disabled do not see the new button even if the shortcut preference was previously enabled.

Tested

• yarn lint
• production yarn build
• verified that the button is rendered only for a single playable file and opens the expected vlc:// stream URL