refactor(api): F.51 — extract playlists + play queue + radio + statistics (#616)

Four more domain-eng modules out of `api/subsonic.ts`:

- `subsonicPlaylists.ts` — `getPlaylists`/`getPlaylist`/`createPlaylist`
  /`updatePlaylist`/`updatePlaylistMeta`/`uploadPlaylistCoverArt`/
  `uploadArtistImage`/`deletePlaylist`. The two upload helpers use
  the Tauri-side CORS bypass (`upload_playlist_cover` /
  `upload_artist_image`).
- `subsonicPlayQueue.ts` — `getPlayQueue`/`savePlayQueue`.
- `subsonicRadio.ts` — Internet Radio CRUD (4 fns), Tauri-side cover
  art ops (3 fns), RadioBrowser search/top + `fetchUrlBytes`.
- `subsonicStatistics.ts` — `fetchStatisticsLibraryAggregates`/
  `fetchStatisticsOverview`/`fetchStatisticsFormatSample` with their
  three per-server-folder caches and the `statisticsPageCacheKey`
  helper. `STATS_CACHE_TTL` renamed from the misleadingly-shared
  `RATING_CACHE_TTL` constant.

Also: drop ~20 now-unused type/value imports from `subsonic.ts`, trim
three orphan jsdoc comments left behind by earlier slices, fix four
`vi.mock` targets (`queueSync`, `playerStore.persistence`) plus the
dynamic `await import('../api/subsonic')` calls in `ContextMenu.tsx`
to point at the new module paths.

Pure code-move. subsonic.ts: 561 → 144 LOC (−417). What's left:
ping/pingWithCredentials/probeInstantMix/scheduleInstantMixProbe +
internal `apiWithCredentials`/`restBaseFromUrl`.

src/pages/ArtistDetail.tsx

@@ -1,3 +1,4 @@
+import { uploadArtistImage } from '../api/subsonicPlaylists';
 import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonicStreamUrl';
 import { setRating, star, unstar } from '../api/subsonicStarRating';
 import { search } from '../api/subsonicSearch';
@@ -7,7 +8,6 @@ import type { SubsonicArtist, SubsonicAlbum, SubsonicSong, SubsonicArtistInfo }
 import { songToTrack } from '../utils/songToTrack';
 import { useEffect, useState, useRef, Fragment, useMemo } from 'react';
 import { useParams, useNavigate } from 'react-router-dom';
-import { uploadArtistImage } from '../api/subsonic';
 import AlbumCard from '../components/AlbumCard';
 import CachedImage from '../components/CachedImage';
 import CoverLightbox from '../components/CoverLightbox';

src/pages/DeviceSync.tsx

@@ -1,3 +1,4 @@
+import { getPlaylists, getPlaylist } from '../api/subsonicPlaylists';
 import { buildDownloadUrl } from '../api/subsonicStreamUrl';
 import { getArtists, getArtist } from '../api/subsonicArtists';
 import { getAlbumList, getAlbum } from '../api/subsonicLibrary';
@@ -15,7 +16,6 @@ import CustomSelect from '../components/CustomSelect';
 import { useTranslation } from 'react-i18next';
 import { useDeviceSyncStore, DeviceSyncSource } from '../store/deviceSyncStore';
 import { useDeviceSyncJobStore } from '../store/deviceSyncJobStore';
-import { getPlaylists, getPlaylist } from '../api/subsonic';
 import { search as searchSubsonic } from '../api/subsonicSearch';
 import { showToast } from '../utils/toast';
 import { IS_WINDOWS } from '../utils/platform';

src/pages/Favorites.tsx

@@ -1,3 +1,4 @@
+import { getInternetRadioStations } from '../api/subsonicRadio';
 import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonicStreamUrl';
 import { getStarred, setRating, unstar } from '../api/subsonicStarRating';
 import type { SubsonicAlbum, SubsonicArtist, SubsonicSong, InternetRadioStation } from '../api/subsonicTypes';
@@ -7,7 +8,6 @@ import { useTracklistColumns, type ColDef } from '../utils/useTracklistColumns';
 import AlbumRow from '../components/AlbumRow';
 import ArtistRow from '../components/ArtistRow';
 import CachedImage from '../components/CachedImage';
-import { getInternetRadioStations } from '../api/subsonic';
 import { usePlayerStore } from '../store/playerStore';
 import { usePreviewStore } from '../store/previewStore';
 import StarRating from '../components/StarRating';

src/pages/InternetRadio.tsx

@@ -1,10 +1,10 @@
+import { getInternetRadioStations, createInternetRadioStation, updateInternetRadioStation, deleteInternetRadioStation, uploadRadioCoverArt, deleteRadioCoverArt, uploadRadioCoverArtBytes, searchRadioBrowser, getTopRadioStations, fetchUrlBytes } from '../api/subsonicRadio';
 import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonicStreamUrl';
 import { type InternetRadioStation, type RadioBrowserStation, RADIO_PAGE_SIZE } from '../api/subsonicTypes';
 import React, { useEffect, useState, useRef, useMemo, useCallback } from 'react';
 import { createPortal } from 'react-dom';
 import { Cast, Plus, Trash2, X, Globe, Camera, Loader2, Search, Heart, Check } from 'lucide-react';
 import { useDragSource, useDragDrop } from '../contexts/DragDropContext';
-import { getInternetRadioStations, createInternetRadioStation, updateInternetRadioStation, deleteInternetRadioStation, uploadRadioCoverArt, deleteRadioCoverArt, uploadRadioCoverArtBytes, searchRadioBrowser, getTopRadioStations, fetchUrlBytes } from '../api/subsonic';
 import { usePlayerStore } from '../store/playerStore';
 import CachedImage from '../components/CachedImage';
 import { invalidateCoverArt } from '../utils/imageCache';

src/pages/PlaylistDetail.tsx

@@ -1,3 +1,4 @@
+import { getPlaylist, updatePlaylist, updatePlaylistMeta, uploadPlaylistCoverArt } from '../api/subsonicPlaylists';
 import { buildDownloadUrl, coverArtCacheKey, buildCoverArtUrl } from '../api/subsonicStreamUrl';
 import { setRating, star, unstar } from '../api/subsonicStarRating';
 import { search } from '../api/subsonicSearch';
@@ -10,7 +11,6 @@ import { useParams, useNavigate, useLocation } from 'react-router-dom';
 import { ChevronDown, ChevronLeft, ChevronRight, Play, ListPlus, Trash2, Search, X, Loader2, Plus, GripVertical, Star, RefreshCw, Shuffle, Heart, HardDriveDownload, Check, Pencil, Globe, Lock, Camera, Download, FileUp, RotateCcw, Sparkles, Square, AudioLines } from 'lucide-react';
 import { useTracklistColumns, type ColDef } from '../utils/useTracklistColumns';
 import { AddToPlaylistSubmenu } from '../components/ContextMenu';
-import { getPlaylist, updatePlaylist, updatePlaylistMeta, uploadPlaylistCoverArt } from '../api/subsonic';
 import { usePlayerStore } from '../store/playerStore';
 import { useShallow } from 'zustand/react/shallow';
 import { usePlaylistStore } from '../store/playlistStore';

src/pages/Playlists.tsx

@@ -1,3 +1,4 @@
+import { deletePlaylist, getPlaylist, updatePlaylist } from '../api/subsonicPlaylists';
 import { getGenres } from '../api/subsonicGenres';
 import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonicStreamUrl';
 import { filterSongsToActiveLibrary } from '../api/subsonicLibrary';
@@ -6,7 +7,6 @@ import { songToTrack } from '../utils/songToTrack';
 import React, { useEffect, useState, useRef, useCallback, useMemo } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { ListMusic, Play, Plus, Trash2, CheckSquare2, Check, Clock3, Sparkles, Pencil } from 'lucide-react';
-import { deletePlaylist, getPlaylist, updatePlaylist } from '../api/subsonic';
 import { usePlayerStore } from '../store/playerStore';
 import { usePlaylistStore } from '../store/playlistStore';
 import { useAuthStore } from '../store/authStore';

src/pages/Statistics.tsx

@@ -1,8 +1,8 @@
+import { fetchStatisticsFormatSample, fetchStatisticsLibraryAggregates, fetchStatisticsOverview } from '../api/subsonicStatistics';
 import { getAlbumList } from '../api/subsonicLibrary';
 import type { SubsonicAlbum, SubsonicGenre } from '../api/subsonicTypes';
 import React, { useEffect, useState } from 'react';
 import { Share2 } from 'lucide-react';
-import { fetchStatisticsFormatSample, fetchStatisticsLibraryAggregates, fetchStatisticsOverview } from '../api/subsonic';
 import { formatHumanHoursMinutes } from '../utils/formatHumanDuration';
 import AlbumRow from '../components/AlbumRow';
 import StatsExportModal from '../components/StatsExportModal';