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/api/subsonicScrobble.test.ts

@@ -0,0 +1,41 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { useAuthStore } from '../store/authStore';
+import { usePlayerStore } from '../store/playerStore';
+import { scrobbleSong } from './subsonicScrobble';
+
+const { apiForServerMock } = vi.hoisted(() => ({
+  apiForServerMock: vi.fn(async () => ({})),
+}));
+
+vi.mock('./subsonicClient', () => ({
+  api: vi.fn(),
+  apiForServer: apiForServerMock,
+}));
+
+describe('subsonicScrobble', () => {
+  beforeEach(() => {
+    apiForServerMock.mockClear();
+    useAuthStore.setState({
+      servers: [
+        { id: 'a', name: 'A', url: 'http://a.test', username: 'u', password: 'p' },
+        { id: 'b', name: 'B', url: 'http://b.test', username: 'u', password: 'p' },
+      ],
+      activeServerId: 'b',
+      isLoggedIn: true,
+    });
+    usePlayerStore.setState({
+      queue: [{ id: 't1', title: 'T', artist: 'A', album: 'Al', albumId: 'al1', duration: 100 }],
+      queueServerId: 'a',
+      queueIndex: 0,
+    });
+  });
+
+  it('scrobbleSong targets the queue server when active server differs', async () => {
+    await scrobbleSong('t1', 1_700_000_000_000, 'a');
+    expect(apiForServerMock).toHaveBeenCalledWith(
+      'a',
+      'scrobble.view',
+      expect.objectContaining({ id: 't1', submission: true, time: 1_700_000_000_000 }),
+    );
+  });
+});