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>

jellyfin/compose.yaml

@@ -0,0 +1,21 @@
+services:
+  jellyfin:
+    image: ${JELLYFIN_IMAGE:-jellyfin/jellyfin:latest}
+    restart: ${JELLYFIN_RESTART:-unless-stopped}
+    volumes:
+      - ${VOL_PATH:-/data}/jellyfin/cache:/cache
+      - ${VOL_PATH:-/data}/jellyfin/config:/config
+      - ${JELLYFIN_MEDIA:-/data/media}/books:/books
+      - ${JELLYFIN_MEDIA:-/data/media}/movies:/movies
+      - ${JELLYFIN_MEDIA:-/data/media}/music:/music
+      - ${JELLYFIN_MEDIA:-/data/media}/shows:/shows
+    environment:
+      - JELLYFIN_PublishedServerUrl=${JELLYFIN_URL:-http://localhost:8096}
+    ports:
+      - "${JELLYFIN_PORT:-8096}:8096"
+    networks:
+      - proxy
+
+networks:
+  proxy:
+    external: true