Retire cancelled playback sessions and preserve VOD content time

Adapted from MikaelKW/nodecast-tv-plus playback lease work beginning at 43a58c7685f541498663b827c4b9d6b3753e7202. Reject superseded requests, release on cancellation, bound live restart attempts and await FFmpeg close before deleting cache.

Co-authored-by: Mikael <mikaelkwessel@gmail.com>

public/js/app.js

@@ -220,6 +220,8 @@ class App {
         logoutLink.addEventListener('click', async (e) => {
             e.preventDefault();
 
+            this.player.stop();
+            this.pages.watch.stop();
             await fetch('/api/auth/logout', { method: 'POST', credentials: 'same-origin' });
 
             localStorage.removeItem('authToken');