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/utils/componentHelpers/miniPlayerHelpers.ts

@@ -58,6 +58,7 @@ export function initialSnapshot(): MiniSyncPayload {
       track: s.currentTrack ? toMini(s.currentTrack) : null,
       queue: (s.queue ?? []).map(toMini),
       queueIndex: s.queueIndex ?? 0,
+      queueServerId: s.queueServerId ?? null,
       isPlaying: s.isPlaying,
       volume: s.volume ?? 1,
       gaplessEnabled: false,
@@ -67,7 +68,7 @@ export function initialSnapshot(): MiniSyncPayload {
     };
   } catch {
     return {
-      track: null, queue: [], queueIndex: 0, isPlaying: false,
+      track: null, queue: [], queueIndex: 0, queueServerId: null, isPlaying: false,
       volume: 1, gaplessEnabled: false, crossfadeEnabled: false,
       infiniteQueueEnabled: false, isMobile: false,
     };