feat: 新增移动客户端（iOS + Android）

- 新增 mobile/ 项目：React Native + Expo
- 5个核心页面：连接服务器、房间列表、创建房间、加入房间、设置
- Tab 导航 + Minecraft 风格深色 UI
- 房间搜索/筛选（名称、房间号、房主、版本类型）
- 15秒自动刷新房间列表
- 设置持久化（AsyncStorage）
- EAS Build 配置（云端构建 iOS/Android）
- 完整 README 含构建指南
- 更新顶层 README 为三项目全平台架构

mobile/App.tsx

@@ -0,0 +1,70 @@
+import React from 'react';
+import { StatusBar } from 'expo-status-bar';
+import { NavigationContainer, DefaultTheme } from '@react-navigation/native';
+import { createBottomTabNavigator } from '@react-navigation/bottom-tabs';
+import { Text, View } from 'react-native';
+import ConnectScreen from './src/screens/ConnectScreen';
+import RoomsScreen from './src/screens/RoomsScreen';
+import CreateScreen from './src/screens/CreateScreen';
+import JoinScreen from './src/screens/JoinScreen';
+import SettingsScreen from './src/screens/SettingsScreen';
+
+const Tab = createBottomTabNavigator();
+
+const DarkTheme = {
+  ...DefaultTheme,
+  colors: {
+    ...DefaultTheme.colors,
+    primary: '#4CAF50',
+    background: '#1a1a2e',
+    card: '#16213e',
+    text: '#e0e0e0',
+    border: 'rgba(15, 52, 96, 0.6)',
+    notification: '#e94560',
+  },
+};
+
+const icons: Record<string, string> = {
+  Connect: '🔗',
+  Rooms: '🎮',
+  Create: '🏠',
+  Join: '🚀',
+  Settings: '⚙️',
+};
+
+export default function App() {
+  return (
+    <NavigationContainer theme={DarkTheme}>
+      <StatusBar style="light" />
+      <Tab.Navigator
+        screenOptions={({ route }) => ({
+          headerStyle: { backgroundColor: '#16213e', elevation: 0, shadowOpacity: 0 },
+          headerTintColor: '#e0e0e0',
+          headerTitleStyle: { fontWeight: '700' },
+          tabBarStyle: {
+            backgroundColor: '#16213e',
+            borderTopColor: 'rgba(15, 52, 96, 0.6)',
+            height: 60,
+            paddingBottom: 8,
+          },
+          tabBarActiveTintColor: '#4CAF50',
+          tabBarInactiveTintColor: '#8a8a9a',
+          tabBarIcon: ({ color }) => (
+            <Text style={{ fontSize: 20 }}>{icons[route.name] || '📱'}</Text>
+          ),
+        })}
+      >
+        <Tab.Screen name="Connect" component={ConnectScreen}
+          options={{ title: '连接', headerTitle: 'FunConnect' }} />
+        <Tab.Screen name="Rooms" component={RoomsScreen}
+          options={{ title: '房间', headerTitle: '房间列表' }} />
+        <Tab.Screen name="Create" component={CreateScreen}
+          options={{ title: '创建', headerTitle: '创建房间' }} />
+        <Tab.Screen name="Join" component={JoinScreen}
+          options={{ title: '加入', headerTitle: '加入房间' }} />
+        <Tab.Screen name="Settings" component={SettingsScreen}
+          options={{ title: '设置', headerTitle: '设置' }} />
+      </Tab.Navigator>
+    </NavigationContainer>
+  );
+}