Prep the Download Center epic (Phase 1 + editor + share) for prod/self-host:
- Dockerfile: create /downloads owned by appuser so a named-volume mount is writable (prod Linux).
- docker-compose.{home,selfhost,yml}: add the 'worker' (yt-dlp/ffmpeg job loop) + 'bgutil-pot'
(PO-token) services + a downloads mount (DOWNLOAD_ROOT, WORKER_ENABLED). Media defaults to a
named volume; DOWNLOAD_HOST_PATH points it at a host dir (e.g. a Plex-readable folder).
- README / docs/self-hosting.md / .env.example / install.{sh,ps1}: document the Download Center,
the two extra containers, and DOWNLOAD_HOST_PATH.
- VERSION 0.22.0 + releaseNotes entry.
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