update greeting

lib/screens/full_screen.dart

@@ -1,4 +1,7 @@
+import 'package:ai_chat_assistant/models/chat_message.dart';
+import 'package:basic_intl/intl.dart';
 import 'package:flutter/material.dart';
+import '../enums/message_status.dart';
 import '../widgets/chat_box.dart';
 import '../widgets/gradient_background.dart';
 import '../services/message_service.dart';
@@ -63,6 +66,14 @@ class _FullScreenState extends State<FullScreen> {
                     WidgetsBinding.instance.addPostFrameCallback((_) {
                       _scrollToBottom();
                     });
+                    final messageService = context.read<MessageService>();
+                    List<ChatMessage> fullScreenMessages = List.from(handler.messages);
+                    if (fullScreenMessages.isEmpty) {
+                      String text = Intl.getCurrentLocale().startsWith('zh')
+                          ? "您好，我是众众，请问有什么可以帮您？"
+                          : "Hi, I'm Zhongzhong, may I help you ? ";
+                      messageService.addMessage(text, false, MessageStatus.normal);
+                    }
                     return ChatBox(
                       scrollController: _scrollController,
                       messages: handler.messages,