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/PlayerBar.tsx

@@ -28,7 +28,7 @@ import PlaybackScheduleBadge from './PlaybackScheduleBadge';
 import { usePlaybackScheduleRemaining } from '../utils/format/playbackScheduleFormat';
 import { usePreviewStore } from '../store/previewStore';
 import { usePerfProbeFlags } from '../utils/perf/perfFlags';
-import { formatTime } from '../utils/componentHelpers/playerBarHelpers';
+import { formatTrackTime } from '../utils/format/formatDuration';
 import { PlaybackTime, RemainingTime } from './playerBar/PlaybackClock';
 import { PlayerTrackInfo } from './playerBar/PlayerTrackInfo';
 import { PlayerTransportControls } from './playerBar/PlayerTransportControls';