feat: add support for pre-request scripts

Introduces `preRequestScript` and `postRequestScript` fields to the request model to store user-defined scripts.

Implements a service using `flutter_js` to execute JavaScript pre-request scripts before a request is sent.
The script can access and modify request data (like headers, body, URL) and environment variables.

Adds bridging to forward JavaScript `console.log`, `console.warn`, and `console.error` calls to the Dart console for easier debugging

lib/models/request_model.g.dart

@@ -27,6 +27,8 @@ _$RequestModelImpl _$$RequestModelImplFromJson(Map json) => _$RequestModelImpl(
       sendingTime: json['sendingTime'] == null
           ? null
           : DateTime.parse(json['sendingTime'] as String),
+      preRequestScript: json['preRequestScript'] as String? ?? "",
+      postRequestScript: json['postRequestScript'] as String? ?? "",
     );
 
 Map<String, dynamic> _$$RequestModelImplToJson(_$RequestModelImpl instance) =>
@@ -39,6 +41,8 @@ Map<String, dynamic> _$$RequestModelImplToJson(_$RequestModelImpl instance) =>
       'responseStatus': instance.responseStatus,
       'message': instance.message,
       'httpResponseModel': instance.httpResponseModel?.toJson(),
+      'preRequestScript': instance.preRequestScript,
+      'postRequestScript': instance.postRequestScript,
     };
 
 const _$APITypeEnumMap = {