refactor(format): consolidate duration formatters into format/formatDuration (Phase L, part 2) (#690)

The mm:ss track-time formatter was hand-rolled in 11 places and the
h:mm:ss total-duration formatter in 4 — extract two tested functions:

- formatTrackTime(seconds, fallback='0:00')  — m:ss, used for track /
  playback times. fallback param covers the '–' placeholder rows.
- formatLongDuration(seconds)                — h:mm:ss when >=1h, else
  m:ss, used for album / queue totals.

Behaviour preserved per call site: the unified guard
(!seconds || !isFinite || <0 -> fallback) produces identical output to
every prior variant for all real inputs; SongRow keeps its '–' via the
fallback arg. Removes the formatter exports from 6 componentHelpers
files (playerBarHelpers / fullscreenPlayerHelpers deleted — they only
exported the formatter) and 7 inline component copies.

+ formatDuration.test.ts

src/components/SongRow.tsx

@@ -8,13 +8,7 @@ import { usePlayerStore } from '../store/playerStore';
 import { enqueueAndPlay } from '../utils/playback/playSong';
 import { useDragDrop } from '../contexts/DragDropContext';
 import { useOrbitSongRowBehavior } from '../hooks/useOrbitSongRowBehavior';
-
-function fmtDuration(s: number): string {
-  if (!s || !isFinite(s)) return '–';
-  const m = Math.floor(s / 60);
-  const sec = Math.floor(s % 60);
-  return `${m}:${sec.toString().padStart(2, '0')}`;
-}
+import { formatTrackTime } from '../utils/format/formatDuration';
 
 interface Props {
   song: SubsonicSong;
@@ -108,7 +102,7 @@ function SongRow({ song }: Props) {
       <div className="song-list-row-cell song-list-row-genre truncate" title={song.genre ?? ''}>
         {song.genre ?? '—'}
       </div>
-      <div className="song-list-row-cell song-list-row-duration">{fmtDuration(song.duration)}</div>
+      <div className="song-list-row-cell song-list-row-duration">{formatTrackTime(song.duration, '–')}</div>
     </div>
   );
 }