implemented backward pagination for chat history with on-scroll prefetching

lib/state/app/modules/chat/bloc/chat_state.g.dart

@@ -12,6 +12,8 @@ _ChatState _$ChatStateFromJson(Map<String, dynamic> json) => _ChatState(
       ? null
       : GetChatResponse.fromJson(json['chatResponse'] as Map<String, dynamic>),
   referenceMessageId: (json['referenceMessageId'] as num?)?.toInt(),
+  hasMoreOld: json['hasMoreOld'] as bool? ?? true,
+  isLoadingOlder: json['isLoadingOlder'] as bool? ?? false,
 );
 
 Map<String, dynamic> _$ChatStateToJson(_ChatState instance) =>
@@ -19,4 +21,6 @@ Map<String, dynamic> _$ChatStateToJson(_ChatState instance) =>
       'currentToken': instance.currentToken,
       'chatResponse': instance.chatResponse,
       'referenceMessageId': instance.referenceMessageId,
+      'hasMoreOld': instance.hasMoreOld,
+      'isLoadingOlder': instance.isLoadingOlder,
     };