media stack: shared /data/media layout, promote sonarr/radarr/jellyfin/jellyseerr

- Promote sonarr, radarr, jellyfin, jellyseerr from _dev
- qBittorrent, Sonarr, Radarr, Lidarr, Readarr, Whisparr mount /data/media
  at /media so paths match across containers (no remote path mappings,
  hardlinks work); downloads go to /media/downloads/prowlarr
- Jellyfin: drop photos (use Immich) and unused internal network, rewrite README
- Jellyseerr: add TZ, document container hostnames and root folders

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

qbittorrent/compose.yaml

@@ -4,7 +4,7 @@ services:
     restart: ${QBT_RESTART:-unless-stopped}
     volumes:
       - ${VOL_PATH:-/data}/qbit/config:/config
-      - ${VOL_PATH:-/data}/qbit/downloads:/downloads
+      - ${QBT_MEDIA:-/data/media}:/media
       - ${VOL_PATH:-/data}/qbit/incomplete:/incomplete
       - ${VOL_PATH:-/data}/qbit/watched:/watched
       - /dev/net/tun:/dev/net/tun