feat(player): stream at the chosen quality + per-track optimize (§6.6)

The Playback quality setting now drives streaming: getStreamUrl appends
?quality= and useAudioPlayer feeds the server-synced streamQuality, so the
backend transcodes on demand (miss → original). Adds an optimizeTrack mutation
and an Optimize action in the metadata editor to warm a track's rendition.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/hooks/useAudioPlayer.ts

@@ -10,6 +10,7 @@ import {
 import { nextTrack, prevTrack } from '../store/slices/queue';
 import { play } from '../store/slices/player';
 import { getStreamUrl, getCoverUrl } from '../api/endpoints/streaming';
+import { useGetSettingsQuery } from '../api/endpoints/settings';
 
 let audioElement: HTMLAudioElement | null = null;
 
@@ -26,6 +27,10 @@ export function useAudioPlayer() {
   const player = useAppSelector((s) => s.player);
   const queue = useAppSelector((s) => s.queue);
   const accessToken = useAppSelector((s) => s.auth.accessToken);
+  // Default stream quality (server-synced §A10) → the backend transcodes to it
+  // on demand; a cache miss transparently falls back to the original.
+  const { data: settings } = useGetSettingsQuery();
+  const streamQuality = settings?.streamQuality;
   const isSetup = useRef(false);
   // `ended` is registered once below; read the latest loop flag through a ref
   // so the listener doesn't need to be re-bound on every queue change.
@@ -63,7 +68,7 @@ export function useAudioPlayer() {
   useEffect(() => {
     if (!player.currentTrackId || !accessToken) return;
     const audio = getAudio();
-    const url = getStreamUrl(player.currentTrackId, accessToken);
+    const url = getStreamUrl(player.currentTrackId, accessToken, streamQuality);
     if (audio.src !== url) {
       audio.src = url;
       audio.load();
@@ -73,7 +78,7 @@ export function useAudioPlayer() {
     } else {
       audio.pause();
     }
-  }, [player.currentTrackId, player.isPlaying, accessToken]);
+  }, [player.currentTrackId, player.isPlaying, accessToken, streamQuality]);
 
   useEffect(() => {
     const audio = getAudio();