Enhance download center with file size preview and dual options

App.tsx

@@ -9,6 +9,7 @@ import SiteManagerModal from './components/SiteManagerModal';
 import HelpModal from './components/HelpModal';
 import { CreateFolderModal, RenameModal, DeleteModal } from './components/FileActionModals';
 import ConflictModal from './components/ConflictModal';
+import DownloadModal from './components/DownloadModal';
 import { formatBytes } from './utils/formatters';
 
 const AdSenseBanner: React.FC = () => {
@@ -58,6 +59,7 @@ const App: React.FC = () => {
   const [showConnectionHelp, setShowConnectionHelp] = useState(false);
   const [showSiteManager, setShowSiteManager] = useState(false);
   const [showHelp, setShowHelp] = useState(false);
+  const [showDownloadModal, setShowDownloadModal] = useState(false);
   const [helpInitialTab, setHelpInitialTab] = useState<'sites' | 'connection' | 'files' | 'backend'>('sites');
   const [savedSites, setSavedSites] = useState<SiteConfig[]>([]);
 
@@ -976,14 +978,13 @@ const App: React.FC = () => {
               </button>
 
               {!(window as any).__IS_STANDALONE__ && (
-                <a
-                  href={`${import.meta.env.BASE_URL}webftp-backend.exe`}
-                  download="webftp-backend.exe"
+                <button
+                  onClick={() => setShowDownloadModal(true)}
                   className={`h-[30px] flex items-center justify-center px-3 rounded bg-emerald-600 hover:bg-emerald-500 text-white border border-emerald-500 shadow-md shadow-emerald-500/20 transition-all ${!connection.connected ? 'animate-pulse ring-2 ring-emerald-400/50' : ''}`}
-                  title="백엔드 다운로드"
+                  title="다운로드 센터"
                 >
-                  <Download size={14} className="mr-1.5" /> 백엔드
-                </a>
+                  <Download size={14} className="mr-1.5" /> 다운로드
+                </button>
               )}
 
               <button
@@ -1089,6 +1090,12 @@ const App: React.FC = () => {
         />
       </div>
 
+      {/* Download Modal - Standalone Only */}
+      <DownloadModal
+        isOpen={showDownloadModal}
+        onClose={() => setShowDownloadModal(false)}
+      />
+
       {/* Footer */}
       <footer className="bg-white border-t border-slate-200 px-3 py-1 text-[10px] text-slate-500 flex justify-between shadow-[0_-2px_10px_rgba(0,0,0,0.02)]">
         <span>WebZilla v1.3.0 <span className="mx-2 text-slate-300">|</span> © SIMP</span>