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/orbit/utils/cleanup.test.ts

@@ -19,7 +19,7 @@ const { authState, orbitState } = vi.hoisted(() => ({
   orbitState: { sessionId: null as string | null },
 }));
 
-vi.mock('@/features/playlist', () => ({ getPlaylists, deletePlaylist }));
+vi.mock('@/lib/api/subsonicPlaylists', () => ({ getPlaylists, deletePlaylist }));
 vi.mock('@/store/authStore', () => ({
   useAuthStore: {
     getState: () => ({

src/features/orbit/utils/cleanup.ts

@@ -1,4 +1,4 @@
-import { deletePlaylist, getPlaylists } from '@/features/playlist';
+import { deletePlaylist, getPlaylists } from '@/lib/api/subsonicPlaylists';
 import { useAuthStore } from '@/store/authStore';
 import { useOrbitStore } from '@/features/orbit/store/orbitStore';
 import { ORBIT_PLAYLIST_PREFIX, parseOrbitState } from '@/features/orbit/api/orbit';

src/features/orbit/utils/guest.ts

@@ -1,4 +1,4 @@
-import { createPlaylist, deletePlaylist, getPlaylist, getPlaylists, updatePlaylist } from '@/features/playlist';
+import { createPlaylist, deletePlaylist, getPlaylist, getPlaylists, updatePlaylist } from '@/lib/api/subsonicPlaylists';
 import { getSong } from '@/lib/api/subsonicLibrary';
 import { songToTrack } from '@/utils/playback/songToTrack';
 import { useAuthStore } from '@/store/authStore';

src/features/orbit/utils/host.test.ts

@@ -24,7 +24,7 @@ vi.mock('@/features/orbit/utils/remote', () => ({
 vi.mock('@/features/orbit/store/orbitStore', () => ({ useOrbitStore: { getState: () => orbitStore } }));
 vi.mock('@/store/authStore', () => ({ useAuthStore: { getState: () => ({}) } }));
 vi.mock('@/store/playerStore', () => ({ usePlayerStore: { getState: () => ({ enqueue: vi.fn() }) } }));
-vi.mock('@/features/playlist', () => ({ createPlaylist: vi.fn(), deletePlaylist: vi.fn() }));
+vi.mock('@/lib/api/subsonicPlaylists', () => ({ createPlaylist: vi.fn(), deletePlaylist: vi.fn() }));
 vi.mock('@/lib/api/subsonicLibrary', () => ({ getSong: vi.fn() }));
 vi.mock('@/utils/playback/songToTrack', () => ({ songToTrack: vi.fn() }));
 

src/features/orbit/utils/host.ts

@@ -1,4 +1,4 @@
-import { createPlaylist, deletePlaylist } from '@/features/playlist';
+import { createPlaylist, deletePlaylist } from '@/lib/api/subsonicPlaylists';
 import { getSong } from '@/lib/api/subsonicLibrary';
 import { songToTrack } from '@/utils/playback/songToTrack';
 import { useAuthStore } from '@/store/authStore';

src/features/orbit/utils/moderation.ts

@@ -1,4 +1,4 @@
-import { deletePlaylist, getPlaylists } from '@/features/playlist';
+import { deletePlaylist, getPlaylists } from '@/lib/api/subsonicPlaylists';
 import { useOrbitStore } from '@/features/orbit/store/orbitStore';
 import { orbitOutboxPlaylistName, type OrbitState } from '@/features/orbit/api/orbit';
 import { writeOrbitState } from '@/features/orbit/utils/remote';

src/features/orbit/utils/remote.ts

@@ -1,4 +1,4 @@
-import { getPlaylist, getPlaylists, updatePlaylistMeta } from '@/features/playlist';
+import { getPlaylist, getPlaylists, updatePlaylistMeta } from '@/lib/api/subsonicPlaylists';
 import {
   orbitSessionPlaylistName,
   parseOrbitState,

src/features/orbit/utils/sweep.ts

@@ -1,4 +1,4 @@
-import { getPlaylist, getPlaylists, updatePlaylist } from '@/features/playlist';
+import { getPlaylist, getPlaylists, updatePlaylist } from '@/lib/api/subsonicPlaylists';
 import { type OrbitOutboxMeta } from '@/features/orbit/api/orbit';
 import { parseOutboxPlaylistName } from '@/features/orbit/utils/helpers';
 import { type OutboxSnapshot } from '@/features/orbit/utils/stateMath';