fix: Replace History with AI Chat in mobile bottom navigation

maternal-web/components/layouts/TabBar/TabBar.tsx

@@ -7,7 +7,7 @@ import {
   Home,
   Timeline,
   Insights,
-  History,
+  Chat,
   Mic,
 } from '@mui/icons-material';
 import { useTranslation } from '@/hooks/useTranslation';
@@ -23,7 +23,7 @@ export const TabBar = () => {
     { label: t('navigation.track'), icon: <Timeline />, value: '/track' },
     { label: '', icon: null, value: 'voice' }, // Placeholder for center button
     { label: t('navigation.insights'), icon: <Insights />, value: '/insights' },
-    { label: t('navigation.history'), icon: <History />, value: '/history' },
+    { label: t('navigation.aiChat'), icon: <Chat />, value: '/ai-assistant' },
   ];
 
   return (