fix: shutdown propre sans erreurs

Problèmes corrigés pendant l'arrêt serveur :
1. RangeError offset bounds : vérification availableSpace avant .set()
2. audioBackend null : vérification avant queueAudio()
3. LiveKit track not found : try/catch sur unpublishTrack

Shutdown maintenant sans erreurs fatales.

client/dev-dist/sw.js

@@ -81,7 +81,7 @@ define(['./workbox-290dd570'], (function (workbox) { 'use strict';
     "revision": "3ca0b8505b4bec776b69afdba2768812"
   }, {
     "url": "index.html",
-    "revision": "0.881sreuemg"
+    "revision": "0.0p0vks93ec8"
   }], {});
   workbox.cleanupOutdatedCaches();
   workbox.registerRoute(new workbox.NavigationRoute(workbox.createHandlerBoundToURL("index.html"), {