- MEDIA_DIR moves to /mnt/data/ytplayer (bind-mounted at /app/bulk); DB, lyrics,
notes and uploads stay on the ytplayer-data volume
- MEDIA_VOLUME_MARKER: while the marker on the drive is missing the cache writes,
serves and deletes nothing, so playback streams and an unmounted drive never
fills the disk under its mountpoint or loses its index on a reboot
- Budget 250 GiB, keep 20 GiB free on the drive
- /api/channel falls back to the uploads playlist and the channel home page when
a channel has no Videos tab (auto-generated '- Topic' music channels)