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]>

app/Models/Video.php

@@ -67,7 +67,9 @@ class Video extends Model
 
     public function audioTracks()
     {
-        return $this->hasMany(\App\Models\VideoAudioTrack::class)->orderBy('id');
+        return $this->hasMany(\App\Models\VideoAudioTrack::class)
+            ->orderBy('position')
+            ->orderBy('id');
     }
 
     public function hasSlideshow(): bool
@@ -252,7 +254,29 @@ class Video extends Model
         if ($realId === null || $realId <= 0) {
             abort(404);
         }
-        return $this->where('id', $realId)->firstOrFail();
+        $video = $this->where('id', $realId)->first();
+        if ($video) {
+            return $video;
+        }
+
+        // Video not found — check the merge-redirect table so old links still work.
+        $redirect = \DB::table('video_redirects')->where('source_id', $realId)->first();
+        if ($redirect) {
+            $target = static::find($redirect->target_id);
+            if ($target) {
+                $newValue = self::encodeId($target->id);
+                $newUrl = preg_replace(
+                    '#/'.preg_quote((string) $value, '#').'(?=/|\?|$)#',
+                    '/'.$newValue,
+                    request()->fullUrl(),
+                    1
+                );
+                throw new \Illuminate\Http\Exceptions\HttpResponseException(
+                    redirect()->to($newUrl, 302)
+                );
+            }
+        }
+        abort(404);
     }
 
     // All share URLs use the unguessable token route