One toast at a time + playback detection fix
Toast queue: now shows one at a time instead of stacking 3. Multiple simultaneous unlocks queue up and play sequentially — each gets its full 10.5s animation and sound before the next one appears.
Playback detection fallback: if window.Events isn't available (varies by Jellyfin build), a MutationObserver now watches for .videoPlayerContainer / video[src] / .htmlVideoPlayer appearing in the DOM and triggers a poll burst. This should fix toasts not showing during video playback on setups where the Jellyfin Events API isn't exposed.