refactor(api): co-locate server-protocol clients into lib/api

Move the Subsonic + Navidrome protocol clients and the library IPC facade
(subsonic*, navidrome*, library.ts + tests) from src/api/ into src/lib/api/,
the feature-free infra layer (plan M4, decision §10.3: shared client core → lib/).
Pure move: deep-path import specifiers @/api/* -> @/lib/api/* across ~150
consumers; no behaviour change. Domain REST (lyrics/events) and cover/analysis
infra stay in src/api/ pending their own M4 placement.

tsc 0, lint 0/0, full suite 319 files / 2353 tests green.

src/features/favorites/components/FavoriteSongRow.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import { useTranslation } from 'react-i18next';
 import { AudioLines, ChevronRight, Play, Square, X } from 'lucide-react';
 import type { ColDef } from '@/utils/useTracklistColumns';
-import type { SubsonicSong } from '@/api/subsonicTypes';
+import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { codecLabel } from '@/utils/componentHelpers/playlistDetailHelpers';
 import { formatLastSeen } from '@/utils/componentHelpers/userMgmtHelpers';
 import i18n from '@/i18n';

src/features/favorites/components/FavoritesSongsSectionHeader.tsx

@@ -1,7 +1,7 @@
 import React, { useMemo, useRef } from 'react';
 import { useTranslation } from 'react-i18next';
 import { ListPlus, Play, SlidersHorizontal, X } from 'lucide-react';
-import type { SubsonicSong } from '@/api/subsonicTypes';
+import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { usePlayerStore } from '@/store/playerStore';
 import { useSelectionStore } from '@/store/selectionStore';
 import { songToTrack } from '@/utils/playback/songToTrack';

src/features/favorites/components/FavoritesSongsTracklist.tsx

@@ -5,7 +5,7 @@ import { TracklistColumnPicker } from '@/components/albumTrackList/TracklistColu
 import { useTranslation } from 'react-i18next';
 import { useNavigate } from 'react-router-dom';
 import type { ColDef } from '@/utils/useTracklistColumns';
-import type { SubsonicSong } from '@/api/subsonicTypes';
+import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { usePlayerStore } from '@/store/playerStore';
 import { previewInputFromSong, usePreviewStore } from '@/store/previewStore';
 import { useSelectionStore } from '@/store/selectionStore';

src/features/favorites/components/RadioFavorites.tsx

@@ -1,7 +1,7 @@
 import React, { useRef, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Cast, ChevronLeft, ChevronRight, Heart, X } from 'lucide-react';
-import type { InternetRadioStation } from '@/api/subsonicTypes';
+import type { InternetRadioStation } from '@/lib/api/subsonicTypes';
 import { CoverArtImage } from '@/cover/CoverArtImage';
 import { albumCoverRef } from '@/cover/ref';
 import { coverArtIdFromRadio } from '@/cover/ids';

src/features/favorites/hooks/useFavoritesData.ts

@@ -1,9 +1,9 @@
 import { useEffect, useMemo, useState } from 'react';
 import { getInternetRadioStations } from '@/features/radio';
-import { getStarred } from '@/api/subsonicStarRating';
+import { getStarred } from '@/lib/api/subsonicStarRating';
 import type {
   InternetRadioStation, SubsonicAlbum, SubsonicArtist, SubsonicSong,
-} from '@/api/subsonicTypes';
+} from '@/lib/api/subsonicTypes';
 import { useAuthStore } from '@/store/authStore';
 import { usePlayerStore } from '@/store/playerStore';
 import type { TopFavoriteArtist } from '@/features/favorites/components/TopFavoriteArtists';

src/features/favorites/hooks/useFavoritesSelection.ts

@@ -1,5 +1,5 @@
 import React, { useCallback, useEffect, useRef } from 'react';
-import type { SubsonicSong } from '@/api/subsonicTypes';
+import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { useSelectionStore } from '@/store/selectionStore';
 
 export interface FavoritesSelectionResult {

src/features/favorites/hooks/useFavoritesSongFiltering.tsx

@@ -1,6 +1,6 @@
 import React, { useMemo } from 'react';
 import { ArrowDown, ArrowUp } from 'lucide-react';
-import type { SubsonicSong } from '@/api/subsonicTypes';
+import type { SubsonicSong } from '@/lib/api/subsonicTypes';
 import { usePlayerStore } from '@/store/playerStore';
 
 const CURRENT_YEAR = new Date().getFullYear();