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/miniPlayer/MiniControls.tsx

@@ -1,5 +1,5 @@
 import { Pause, Play, SkipBack, SkipForward } from 'lucide-react';
-import { fmt } from '../../utils/componentHelpers/miniPlayerHelpers';
+import { formatTrackTime } from '../../utils/format/formatDuration';
 import type { MiniControlAction } from '../../utils/miniPlayerBridge';
 
 interface Props {
@@ -26,11 +26,11 @@ export function MiniControls({ isPlaying, currentTime, duration, progress, contr
       </div>
 
       <div className="mini-player__progress">
-        <div className="mini-player__progress-time">{fmt(currentTime)}</div>
+        <div className="mini-player__progress-time">{formatTrackTime(currentTime)}</div>
         <div className="mini-player__progress-track">
           <div className="mini-player__progress-fill" style={{ width: `${progress}%` }} />
         </div>
-        <div className="mini-player__progress-time">{fmt(duration)}</div>
+        <div className="mini-player__progress-time">{formatTrackTime(duration)}</div>
       </div>
     </div>
   );