feat(playback): HLS VOD rendition for browser (supplements MP4 proxy)
Browser playback of recorded assets moves to HLS, retiring the MP4
range-stitching path for VOD. MP4 proxy is kept for the Premiere panel.
- worker/hls.js: remuxToHls() stream-copies the proxy MP4 → fMP4 HLS
(playlist.m3u8 + init.mp4 + segment_*.m4s) via existing segmentToHls,
uploads to hls/<id>/, sets assets.hls_s3_key. hlsWorker backfills from
an existing proxy.
- proxy.js: generate HLS inline after the MP4 upload (local file, no
re-download, no re-encode); best-effort/non-fatal.
- worker/index.js: register 'hls' worker wherever 'proxy' runs.
- mam-api: GET /assets/:id/hls/:file serves playlist/init/segments as
whole-object GETs (no Range → sidesteps RustFS bug), strict filename
validation. /stream prefers hls_s3_key (type:'hls'). reprocess?type=hls
backfills. Migration 025 adds assets.hls_s3_key.
- Frontend unchanged: hls.js path already handles type:'hls'.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>