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>

CLAUDE.md

@@ -24,6 +24,7 @@ Root `compose.yaml` uses Docker Compose's `include` directive to orchestrate mul
 - **joplin**: Joplin Server note-taking and sync platform (PostgreSQL)
 - **vert**: VERT file format converter (WebAssembly-based, stateless)
 - **paint**: miniPaint web-based image editor (built from GitHub)
+- **jelly**: Jellyfin media server with hardware transcoding
 - **restic**: Backrest backup system with restic backend
 - **sablier**: Dynamic scaling plugin for Traefik
 - **vpn**: WireGuard VPN (wg-easy)
@@ -294,6 +295,33 @@ Access https://paint.pivoine.art to use the image editor. All editing happens in
 
 **Note**: miniPaint is stateless and doesn't require backups as no data is persisted.
 
+### Jellyfin (jelly/compose.yaml)
+Jellyfin media server for streaming photos and videos:
+- **jellyfin**: Jellyfin app exposed at `jelly.pivoine.art:8096`
+  - Self-hosted media streaming server
+  - Hardware transcoding support for video playback
+  - Automatic media library organization with metadata
+  - Multi-device support (web, mobile apps, TV apps)
+  - User management with watch history and favorites
+  - Subtitle support and on-the-fly transcoding
+  - Data persisted in `jellyfin_config` and `jellyfin_cache` volumes
+
+**Media Sources**:
+- **Pictures**: `/mnt/hidrive/users/valknar/Pictures` (read-only)
+- **Videos**: `/mnt/hidrive/users/valknar/Videos` (read-only)
+- Uses HiDrive WebDAV mount via davfs2 on host
+
+**Configuration**:
+- First access: Create admin account at https://jelly.pivoine.art
+- Add media libraries pointing to `/media/pictures` and `/media/videos`
+- Configure transcoding settings in Dashboard → Playback
+- Enable hardware acceleration if available
+
+**Usage**:
+Access https://jelly.pivoine.art to browse and stream your media. Jellyfin will automatically organize your content, fetch metadata, and provide optimized streaming to any device.
+
+**Note**: Jellyfin requires the HiDrive WebDAV mount to be active on the host at `/mnt/hidrive`.
+
 ### Restic (restic/compose.yaml)
 Backrest backup system with restic backend:
 - **backrest**: Backrest web UI exposed at `restic.pivoine.art:9898`