refactor(utils): split componentHelpers grab-bag to owning layers

Per-file routing of the 9-file utils/componentHelpers grab-bag, each driven by
its verified consumer set:
- contextMenu{Actions,Helpers} → features/contextMenu/utils (sole consumer)
- queuePanelHelpers → features/queue/utils (sole consumer)
- nowPlayingHelpers → features/nowPlaying/utils; isRealArtistImage split out to
  cover/ (consumed by cover/artistHero, a lower layer)
- appUpdaterHelpers(+test) + listReorder(+test) → lib/util (config/ + lib/hooks
  consume them; pure)
- playlistDetailHelpers → lib/format (consumed by 3 features; pure)
- appShellHelpers → app/ (app-shell consumers only)
- userMgmtHelpers left in place: consumed by the a11y-HELD SongInfoModal, so a
  move would rewrite a do-not-touch file (same block as licensesData).

Pure moves; tests pass unmodified.

src/features/contextMenu/components/MultiArtistToPlaylistSubmenu.tsx

@@ -9,7 +9,7 @@ import { showToast } from '@/lib/dom/toast';
 import {
   confirmAddAllDuplicates,
   isSmartPlaylistName,
-} from '@/utils/componentHelpers/contextMenuHelpers';
+} from '@/features/contextMenu/utils/contextMenuHelpers';
 
 interface Props {
   artistIds: string[];