feat(frontend): 菜单组件 — 主菜单/本地双人/AI设置/网络/加载棋谱

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/components/menu/MainMenu.tsx

@@ -0,0 +1,34 @@
+import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
+import LocalGameSetup from './LocalGameSetup';
+import AiGameSetup from './AiGameSetup';
+import OnlineSetup from './OnlineSetup';
+import LoadReplay from './LoadReplay';
+
+type View = 'main' | 'local' | 'ai' | 'online' | 'replay';
+
+interface Props {
+  onGameStart: () => void;
+}
+
+export default function MainMenu({ onGameStart }: Props) {
+  const { t } = useTranslation();
+  const [view, setView] = useState<View>('main');
+
+  if (view === 'local') return <LocalGameSetup onBack={() => setView('main')} onStart={onGameStart} />;
+  if (view === 'ai') return <AiGameSetup onBack={() => setView('main')} onStart={onGameStart} />;
+  if (view === 'online') return <OnlineSetup onBack={() => setView('main')} onStart={onGameStart} />;
+  if (view === 'replay') return <LoadReplay onBack={() => setView('main')} onStart={onGameStart} />;
+
+  return (
+    <div className="main-menu">
+      <h1 className="menu-title">{t('app.title')}</h1>
+      <div className="menu-buttons">
+        <button onClick={() => setView('local')}>{t('menu.local_game')}</button>
+        <button onClick={() => setView('ai')}>{t('menu.ai_game')}</button>
+        <button onClick={() => setView('online')}>{t('menu.online_game')}</button>
+        <button onClick={() => setView('replay')}>{t('menu.load_replay')}</button>
+      </div>
+    </div>
+  );
+}