refactor(utils): group utils/ files into topic folders (Phase L, part 1) (#689)

111 of 122 top-level src/utils/ files move into 16 topic folders (audio,
cache, cover, share, server, playback, playlist, deviceSync, waveform,
mix, format, export, changelog, ui, perf, componentHelpers). True
singletons with no cluster stay at the utils/ root.

Pure file-move: a path-aware codemod rewrote 539 relative-import
specifiers across 275 files; no logic touched. The hot-path coverage
gate list (.github/frontend-hot-path-files.txt) is updated to the new
paths for the 11 gated utils files — a mechanical consequence of the
move, not a CI change. tsc is green.

src/utils/componentHelpers/appUpdaterHelpers.ts

@@ -0,0 +1,53 @@
+import { IS_LINUX, IS_MACOS, IS_WINDOWS } from '../platform';
+
+export const SKIP_KEY = 'psysonic_skipped_update_version';
+
+// Semver comparison: returns true if `a` is newer than `b`
+export function isNewer(a: string, b: string): boolean {
+  const pa = a.replace(/^[^0-9]*/, '').split('.').map(Number);
+  const pb = b.replace(/^[^0-9]*/, '').split('.').map(Number);
+  for (let i = 0; i < 3; i++) {
+    if ((pa[i] ?? 0) > (pb[i] ?? 0)) return true;
+    if ((pa[i] ?? 0) < (pb[i] ?? 0)) return false;
+  }
+  return false;
+}
+
+export function fmtBytes(n: number): string {
+  if (n < 1024 * 1024) return `${(n / 1024).toFixed(0)} KB`;
+  return `${(n / 1024 / 1024).toFixed(1)} MB`;
+}
+
+export interface GithubAsset {
+  name: string;
+  browser_download_url: string;
+  size: number;
+}
+
+export interface ReleaseData {
+  version: string;
+  tag: string;
+  body: string;
+  assets: GithubAsset[];
+}
+
+export type DlState = 'idle' | 'downloading' | 'done' | 'error';
+
+export function pickAsset(assets: GithubAsset[]): GithubAsset | undefined {
+  if (IS_WINDOWS) {
+    return assets.find(a => a.name.endsWith('-setup.exe'))
+      ?? assets.find(a => a.name.endsWith('.exe'));
+  }
+  if (IS_MACOS) {
+    // Prefer Apple Silicon, fall back to Intel
+    return assets.find(a => a.name.endsWith('.dmg') && a.name.includes('aarch64'))
+      ?? assets.find(a => a.name.endsWith('.dmg'));
+  }
+  if (IS_LINUX) {
+    // AppImage > deb > rpm
+    return assets.find(a => a.name.endsWith('.AppImage'))
+      ?? assets.find(a => a.name.endsWith('.deb'))
+      ?? assets.find(a => a.name.endsWith('.rpm'));
+  }
+  return undefined;
+}