Chunked uploads: bypass Cloudflare's 100 MB request cap by slicing the
video/audio into 8 MB chunks and reassembling server-side before the
normal store flow runs.
Track reorder: audio tracks gain a `position` column so a user's edit-
modal ordering survives reload. `Video::audioTracks()` now orders by
position, `promote_track_id` remembers the swapped row, and freshly
uploaded tracks append to the end.
Playlist per-track pinning: `playlist_videos.audio_track_id` remembers
which language the user pinned when adding a song. Same song with a
different track becomes a separate row (Spotify-style duplicates).
Player-data exposes `active_stream_url` + `active_track_id`, sidebar
cards render `?track=` from the pivot, and both `plTransitionTo` and
initial-load code activate the corresponding language option.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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