feat(apps): 重构 UI 架构为 presentation 层并新增 l10n 国际化支持

apps/lib/shared/widgets/chat_bubble.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import '../../../core/l10n/l10n.dart';
 import '../../../core/theme/design_tokens.dart';
 
 enum MessageSender { user, ai }
@@ -77,11 +78,11 @@ class ChatBubble extends StatelessWidget {
 
     String dateStr;
     if (msgDate == today) {
-      dateStr = '今天';
+      dateStr = L10n.current.chatTimestampToday;
     } else if (msgDate == today.subtract(const Duration(days: 1))) {
-      dateStr = '昨天';
+      dateStr = L10n.current.chatTimestampYesterday;
     } else {
-      dateStr = '${time.month}月${time.day}日';
+      dateStr = L10n.current.chatTimestampMonthDay(time.month, time.day);
     }
 
     final timeStr =