refactor(version_update): 移除未使用的渠道变量并优化日志输出

- 注释掉未使用的_channel赋值
- 为iOS设备设置默认渠道
- 优化日志输出格式，添加开发者前缀

lib/data/services/version_update_service.dart

@@ -117,7 +117,7 @@ class VersionUpdateService extends GetxService {
       final platformInfo = await getCurrentPlatformInfo();
 
       _platform = platformInfo.platform;
-      _channel = platformInfo.channel;
+      //_channel = platformInfo.channel;
       _lastCheckTime = DateTime.now();
 
       // 调用后端接口获取最新版本信息
@@ -147,6 +147,7 @@ class VersionUpdateService extends GetxService {
 
       // 设置游客登录显示状态（先用当前渠道结果作为回退，再用.env渠道覆盖以保持一致）
       _isShowTourists = appInfo.tourists;
+      //print('lxm--_isShowTourists: $_isShowTourists');
       if (Platform.isAndroid && _channel != platformInfo.channel) {
         //[4]当前渠道与.env渠道不同，需要从.env渠道获取游客登录配置
         await _refreshTouristsFromEnv();
@@ -211,6 +212,7 @@ class VersionUpdateService extends GetxService {
   /// 获取当前平台信息
   Future<PlatformInfo> getCurrentPlatformInfo() async {
     if (Platform.isIOS) {
+      _channel = UserChannel.GLOBAL_APPLE;
       await _getIosDeviceBrand();
       return const PlatformInfo(
         platform: 'ios',
@@ -302,7 +304,7 @@ class VersionUpdateService extends GetxService {
         final envAppInfo = AppInfo.fromJson(resp['app']);
         _isShowTourists = envAppInfo.tourists;
         _logger.d(
-            '游客登录配置已按.env渠道同步: ${envAppInfo.tourists} (channel=$envChannelName)');
+            'lxm--游客登录配置已按.env渠道同步: ${envAppInfo.tourists} (channel=$envChannelName)');
       } else {
         _logger.w('按.env渠道获取游客配置失败：响应为空或不含app字段');
       }