music: per-device now-playing (browser vs phone)

Key music_now_playing on (user_id, device) instead of user_id alone so the
browser ('web') and phone ('' default) each keep their own resume snapshot
instead of sharing one row. Sidecar /now-playing threads device (?device=,
default '') through get/set/clearNowPlaying; the web client tags its calls
?device=web. Phone unchanged → '' bucket, inherits the existing row.

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

src/workspaces/officerdev/src/MusicPlayer/MusicPlayerHost.tsx

@@ -76,7 +76,7 @@ export const MusicPlayerHost = () => {
 
   const persist = () => {
     if (!current) return;
-    put('/music/now-playing', {
+    put('/music/now-playing?device=web', {
       homePath: trackHomePath(current.albumRel, current.file),
       dir: `Music/${current.albumRel}`,
       title: current.title ?? '',
@@ -126,7 +126,7 @@ export const MusicPlayerHost = () => {
     restoredRef.current = true;
     if (queue.length) return;
     (async () => {
-      const snap = await get<NowPlaying | null>('/music/now-playing').catch(() => null);
+      const snap = await get<NowPlaying | null>('/music/now-playing?device=web').catch(() => null);
       if (!snap?.homePath) return;
       const albumRel = (snap.dir || snap.homePath.split('/').slice(0, -1).join('/')).replace(/^Music\//, '');
       const file = snap.homePath.split('/').pop() ?? '';
@@ -236,7 +236,7 @@ export const MusicPlayerHost = () => {
   // Closing the dock also clears the saved "currently playing" snapshot, so it doesn't get restored on
   // the next load. (Merely close()-ing the local queue would leave the server snapshot to bring it back.)
   const handleClose = () => {
-    del('/music/now-playing').catch(() => {});
+    del('/music/now-playing?device=web').catch(() => {});
     close();
   };