Add four new integrations with full widget support:
- Uptime Kuma: dashboard monitors, uptime percentage ring, status counts
- Audiobookshelf: library stats, audiobooks/podcasts counts, listening time
- Paperless-ngx: document stats, inbox ratio ring, correspondents/tags
- Navidrome: artist/album/song counts, now playing with track list
Also adds a unified "Audio Stats" widget that merges Navidrome and
Audiobookshelf into a single configurable widget with backend-specific
option visibility.
Includes Vitest specs for pagination, status mapping, and shared utils.