feat: 添加 openim_common 依赖，重构环境配置和主页 URL 获取逻辑

lib/config/app_config.dart

@@ -1,18 +1,8 @@
-enum Environment {
-  production,
-}
+import 'package:openim_common/openim_common.dart' as openim_common;
 
 class AppConfig {
-  static const Environment currentEnvironment = Environment.production;
-
-  static final Map<Environment, List<String>> _environmentHosts = {
-    Environment.production: [
-      'h5-im.imharry.work',
-    ],
-  };
-
   static List<String> get environmentHosts {
-    return _environmentHosts[currentEnvironment] ?? const [];
+    return openim_common.Config.environmentHosts;
   }
 
   static String get homeUrl {