feat(desktop): PC·업데이트 팝업 Apple/Windows 브랜드 아이콘

Co-authored-by: Cursor <cursoragent@cursor.com>

desktop/src/StartupUpdateGate.tsx

@@ -5,6 +5,8 @@ import {
   type DesktopUpdateProgress,
 } from './bridge/updater';
 import { scheduleMainWindowTitleSync } from './setMainWindowTitle';
+import { PlatformBrandIcon, type PlatformBrandIconId } from '@frontend/components/icons/PlatformBrandIcons';
+import { isMacDesktop, isWindowsDesktop } from '@frontend/utils/platform';
 import '@frontend/App.css';
 
 const PHASE_LABEL: Record<DesktopUpdatePhase, string> = {
@@ -35,9 +37,20 @@ function StartupUpdateSplash({ progress }: { progress: DesktopUpdateProgress | n
       ? 'desktop-update-progress--active'
       : '';
 
+  const platformBrand: PlatformBrandIconId | null = isMacDesktop()
+    ? 'mac'
+    : isWindowsDesktop()
+      ? 'windows'
+      : null;
+
   return (
     <div className="desktop-startup-update">
       <div className="desktop-startup-update-card">
+        {platformBrand && (
+          <div className="desktop-update-platform-brand desktop-update-platform-brand--startup">
+            <PlatformBrandIcon platform={platformBrand} />
+          </div>
+        )}
         <h1 className="desktop-startup-update-title">GoldenChart</h1>
         <p className="desktop-startup-update-sub">
           {progress?.currentVersion ? `현재 v${progress.currentVersion}` : '시작 중…'}