feat: 添加媒体权限请求桥接脚本，优化 WebView 媒体权限处理逻辑

lib/config/app_config.dart

@@ -41,7 +41,8 @@ class AppConfig {
   }) {
     final uri = Uri.parse(url);
     final queryParameters = Map<String, String>.from(uri.queryParameters)
-      ..['flutter_shell'] = '1';
+      ..['flutter_shell'] = '1'
+      ..['shell_cache_bust'] = DateTime.now().millisecondsSinceEpoch.toString();
 
     final trimmedName = (appName ?? AppConfig.appName).trim();
     if (trimmedName.isNotEmpty) {