MPEG-TS segments cannot carry AV1, so a Jellyfin server with an AV1
hardware encoder (Intel Arc and similar) could never pick AV1 as the
transcode output no matter what the codec list advertised. Switch the
video TranscodingProfile container from ts to mp4, matching
jellyfin-web's fMP4 HLS behavior; mpv consumes fMP4 HLS on every
platform and the Plex VOD target has shipped it since issue #1859.
close#2131