- First play: stream fragmented MP4 from ffmpeg stdout (instant start)
  while simultaneously caching to disk
- Subsequent plays: serve cached file with full byte-range/seeking
- Silence mdns_sd debug/info log spam
- Remove Done button from cast view
- Slower backdrop crossfade (2s) on library page

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>