refactor(api): pull feature-resident subsonic clients into lib/api

Move the 5 subsonic api modules that M3 had co-located into features
(subsonicAlbumInfo/Artists/Playlists/Radio/Statistics) into src/lib/api/, the
feature-free infra layer, and drop their feature-barrel re-exports. Consumers
now import these protocol calls directly from @/lib/api/subsonic*; the feature
barrels export only domain UI/hooks/state.

This is the consistent api placement (plan §10.3, revised: ALL subsonic protocol
clients are feature-free infra, not per-feature) and it kills the documented
api-induced feature<->feature cycles: offline->artist/playlist (getArtist/
getPlaylist*), album->artist (getArtistInfo), deviceSync/nowPlaying/orbit->*.
Remaining artist<->album refs are UI-only (OpenArtistRefInline/coerceOpenArtist
Refs) and offline->playlist is store-level (usePlaylistStore) — both deeper,
tracked for M5, not api placement.

Pure move: import specifiers + vi.mock/spy targets repointed; no behaviour
change. tsc 0, lint 0/0, full suite 319 files / 2353 tests green.

Tooling note: barrel-imported and dynamic-import api symbols were split out of
@/features/* to @/lib/api/* (tsc-driven); 12 vi.mock barrels retargeted to the
deep lib module (mock-collapse sweep), AlbumHeader's UI mock left untouched.

src/features/nowPlaying/components/NowPlayingInfo.tsx

@@ -1,5 +1,5 @@
 import { getSongForServer } from '@/lib/api/subsonicLibrary';
-import { getArtistInfoForServer } from '@/features/artist';
+import { getArtistInfoForServer } from '@/lib/api/subsonicArtists';
 import type { SubsonicArtistInfo, SubsonicSong } from '@/lib/api/subsonicTypes';
 import React, { useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
 import { useTranslation } from 'react-i18next';

src/features/nowPlaying/hooks/useNowPlayingFetchers.test.ts

@@ -13,7 +13,7 @@ import { renderHook, act, waitFor } from '@testing-library/react';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 import type { SubsonicArtistInfo, SubsonicSong, SubsonicAlbum, SubsonicArtist } from '@/lib/api/subsonicTypes';
 
-vi.mock('@/features/artist');
+vi.mock('@/lib/api/subsonicArtists');
 vi.mock('@/lib/api/subsonicLibrary');
 vi.mock('@/api/bandsintown');
 vi.mock('@/utils/network/subsonicNetworkGuard', () => ({
@@ -21,7 +21,7 @@ vi.mock('@/utils/network/subsonicNetworkGuard', () => ({
 }));
 
 import { shouldAttemptSubsonicForServer } from '@/utils/network/subsonicNetworkGuard';
-import { getArtistForServer, getArtistInfoForServer, getTopSongsForServer } from '@/features/artist';
+import { getArtistForServer, getArtistInfoForServer, getTopSongsForServer } from '@/lib/api/subsonicArtists';
 import { getAlbumForServer, getSongForServer } from '@/lib/api/subsonicLibrary';
 import { fetchBandsintownEvents } from '@/api/bandsintown';
 import { useNowPlayingFetchers, type NowPlayingFetchersDeps } from '@/features/nowPlaying/hooks/useNowPlayingFetchers';

src/features/nowPlaying/hooks/useNowPlayingFetchers.ts

@@ -1,5 +1,5 @@
 import { useEffect, useState } from 'react';
-import { getArtistInfoForServer } from '@/features/artist';
+import { getArtistInfoForServer } from '@/lib/api/subsonicArtists';
 import type { SubsonicAlbum, SubsonicArtistInfo, SubsonicSong } from '@/lib/api/subsonicTypes';
 import { resolveNpAlbum, resolveNpDiscography, resolveNpSongMeta, resolveNpTopSongs } from '@/features/nowPlaying/utils/nowPlayingMetadataResolve';
 import { fetchBandsintownEvents, type BandsintownEvent } from '@/api/bandsintown';

src/features/nowPlaying/utils/nowPlayingMetadataResolve.test.ts

@@ -9,7 +9,7 @@ import { describe, it, expect, beforeEach, vi } from 'vitest';
 import { onInvoke } from '@/test/mocks/tauri';
 import { useLibraryIndexStore } from '@/store/libraryIndexStore';
 import type { LibraryAdvancedSearchResponse } from '@/lib/api/library';
-import * as subsonicArtists from '@/features/artist';
+import * as subsonicArtists from '@/lib/api/subsonicArtists';
 import * as subsonicLibrary from '@/lib/api/subsonicLibrary';
 
 // Network reachability is decided by the guard; mock it so we can test both arms.

src/features/nowPlaying/utils/nowPlayingMetadataResolve.ts

@@ -17,7 +17,7 @@
  * is intentionally absent here.
  */
 import { libraryGetTrack, libraryGetTracksByAlbum } from '@/lib/api/library';
-import { getArtistForServer, getTopSongsForServer } from '@/features/artist';
+import { getArtistForServer, getTopSongsForServer } from '@/lib/api/subsonicArtists';
 import { getAlbumForServer, getSongForServer } from '@/lib/api/subsonicLibrary';
 import type { SubsonicAlbum, SubsonicSong } from '@/lib/api/subsonicTypes';
 import { shouldAttemptSubsonicForServer } from '@/utils/network/subsonicNetworkGuard';