feat: add Jellyfin media server (jelly.pivoine.art)

Added Jellyfin stack for streaming photos and videos from HiDrive:
- Maps /mnt/hidrive/users/valknar/Pictures to /media/pictures (read-only)
- Maps /mnt/hidrive/users/valknar/Videos to /media/videos (read-only)
- Hardware transcoding support for optimal video playback
- Multi-device streaming (web, mobile, TV apps)
- Automatic media organization with metadata fetching

Jellyfin provides superior video playback compared to Filestash's
transcoding plugin, which has compatibility issues with named pipes
in containerized environments.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

arty.yml

@@ -120,6 +120,10 @@ envs:
     PAINT_TRAEFIK_ENABLED: true
     PAINT_COMPOSE_PROJECT_NAME: paint
     PAINT_TRAEFIK_HOST: paint.pivoine.art
+    # Jellyfin
+    JELLY_TRAEFIK_ENABLED: true
+    JELLY_COMPOSE_PROJECT_NAME: jelly
+    JELLY_TRAEFIK_HOST: jelly.pivoine.art
     # Proxy
     PROXY_COMPOSE_PROJECT_NAME: proxy
     PROXY_DOCKER_IMAGE: traefik:latest