Chunked video upload, persistent track order, per-track playlist entries

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) <[email protected]>

resources/views/layouts/partials/edit-video-modal.blade.php

@@ -980,6 +980,14 @@ document.getElementById('edit-form').addEventListener('submit', function(e) {
     // Append delete IDs
     _editDeleteTrackIds.forEach(id => formData.append('delete_track_ids[]', id));
 
+    // Ordered list of track IDs as displayed. Index 0 is the primary slot;
+    // "primary" is the sentinel for the original primary track row, since
+    // the primary isn't a video_audio_tracks row of its own.
+    Array.from(document.querySelectorAll('#edit-tc-list > .um-track-card')).forEach(card => {
+        const val = (card.id === 'edit-tc-t1-card') ? 'primary' : (card.dataset.trackId || '');
+        if (val) formData.append('track_order[]', val);
+    });
+
     // ── Log tracker: dump the exact track-related payload being submitted ──────
     (function () {
         const promoteId = document.getElementById('edit-promote-track-id')?.value || '(none)';