fix(playback): pin queue playback to source server when browsing another library (#717)

* fix(playback): pin queue streams, cover art, and library links to queue server

When the active server changes while a queue from another server is playing,
keep streams and UI on queueServerId; switch back for artist/album links and
queue or player-bar context menus.

* fix(playback): switch to queue server when opening Now Playing

Ensure active server matches queueServerId before Subsonic fetches on the
Now Playing page, mobile player route, and queue info panel; scope caches
by server id.

* docs(credits): mention Now Playing in PR #717 contribution line

* fix(playback): route scrobble and queue sync to queue server

Address PR review: apiForServer for scrobble/now-playing/savePlayQueue,
clear queueServerId on server removal, mini-player queueServerId sync,
block cross-server enqueue with toast, and regression tests.

src/locales/zh/queue.ts

@@ -28,6 +28,7 @@ export const queue = {
   shareQueue: '复制队列分享链接',
   shareQueueEmpty: '队列为空，无法分享。',
   emptyQueue: '队列为空。',
+  crossServerEnqueueBlocked: '无法将其他服务器的曲目加入当前播放队列。请先清空或结束当前队列。',
   trackSingular: '首曲目',
   trackPlural: '首曲目',
   showRemaining: '显示剩余时间',