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/OrbitSessionBar.tsx

@@ -19,6 +19,7 @@ import OrbitSettingsPopover from './OrbitSettingsPopover';
 import OrbitSharePopover from './OrbitSharePopover';
 import OrbitDiagnosticsPopover from './OrbitDiagnosticsPopover';
 import ConfirmModal from './ConfirmModal';
+import { formatTrackTime } from '../utils/format/formatDuration';
 
 /**
  * Orbit — top-strip session indicator.
@@ -34,11 +35,9 @@ import ConfirmModal from './ConfirmModal';
 
 const CATCH_UP_DRIFT_THRESHOLD_MS = 3_000;
 
+/** `m:ss` countdown from a millisecond value. */
 function formatCountdown(ms: number): string {
-  const clamped = Math.max(0, Math.round(ms / 1000));
-  const m = Math.floor(clamped / 60);
-  const s = clamped % 60;
-  return `${m}:${s.toString().padStart(2, '0')}`;
+  return formatTrackTime(Math.round(ms / 1000));
 }
 
 export default function OrbitSessionBar() {