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/fullscreenPlayer/FsSeekbar.tsx

@@ -1,7 +1,7 @@
 import React, { memo, useCallback, useEffect, useRef } from 'react';
 import { usePlayerStore } from '../../store/playerStore';
 import { getPlaybackProgressSnapshot, subscribePlaybackProgress } from '../../store/playbackProgress';
-import { formatTime } from '../../utils/componentHelpers/fullscreenPlayerHelpers';
+import { formatTrackTime } from '../../utils/format/formatDuration';
 
 // Full-width seekbar — imperative DOM updates, zero React re-renders on tick.
 export const FsSeekbar = memo(function FsSeekbar({ duration }: { duration: number }) {
@@ -19,7 +19,7 @@ export const FsSeekbar = memo(function FsSeekbar({ duration }: { duration: numbe
     pendingSeekRef.current = p;
     if (timeRef.current) {
       const previewTime = duration > 0 ? p * duration : s.currentTime;
-      timeRef.current.textContent = formatTime(previewTime);
+      timeRef.current.textContent = formatTrackTime(previewTime);
     }
     if (playedRef.current) playedRef.current.style.width = `${p * 100}%`;
     if (bufRef.current) bufRef.current.style.width = `${Math.max(p * 100, s.buffered * 100)}%`;
@@ -36,7 +36,7 @@ export const FsSeekbar = memo(function FsSeekbar({ duration }: { duration: numbe
   useEffect(() => {
     const s = getPlaybackProgressSnapshot();
     const pct = s.progress * 100;
-    if (timeRef.current)   timeRef.current.textContent  = formatTime(s.currentTime);
+    if (timeRef.current)   timeRef.current.textContent  = formatTrackTime(s.currentTime);
     if (playedRef.current) playedRef.current.style.width = `${pct}%`;
     if (bufRef.current)    bufRef.current.style.width    = `${Math.max(pct, s.buffered * 100)}%`;
     if (inputRef.current)  inputRef.current.value        = String(s.progress);
@@ -44,7 +44,7 @@ export const FsSeekbar = memo(function FsSeekbar({ duration }: { duration: numbe
     return subscribePlaybackProgress(state => {
       if (isDraggingRef.current) return;
       const p = state.progress * 100;
-      if (timeRef.current)   timeRef.current.textContent  = formatTime(state.currentTime);
+      if (timeRef.current)   timeRef.current.textContent  = formatTrackTime(state.currentTime);
       if (playedRef.current) playedRef.current.style.width = `${p}%`;
       if (bufRef.current)    bufRef.current.style.width    = `${Math.max(p, state.buffered * 100)}%`;
       if (inputRef.current)  inputRef.current.value        = String(state.progress);
@@ -62,7 +62,7 @@ export const FsSeekbar = memo(function FsSeekbar({ duration }: { duration: numbe
     <div className="fs-seekbar-wrap">
       <div className="fs-seekbar-times">
         <span ref={timeRef} />
-        <span>{formatTime(duration)}</span>
+        <span>{formatTrackTime(duration)}</span>
       </div>
       <div className="fs-seekbar">
         <div className="fs-seekbar-bg" />