feat: 优化 AI 教练聊天和打卡功能

- 在 AI 教练聊天界面中添加会话缓存功能，支持冷启动时恢复聊天记录
- 实现轻量防抖机制，确保会话变动时及时保存缓存
- 在打卡功能中集成按月加载打卡记录，提升用户体验
- 更新 Redux 状态管理，支持打卡记录的按月加载和缓存
- 新增打卡日历页面，允许用户查看每日打卡记录
- 优化样式以适应新功能的展示和交互

app/checkin/index.tsx

@@ -3,7 +3,7 @@ import { Colors } from '@/constants/Colors';
 import { useAppDispatch, useAppSelector } from '@/hooks/redux';
 import { useColorScheme } from '@/hooks/useColorScheme';
 import type { CheckinExercise } from '@/store/checkinSlice';
-import { getDailyCheckins, removeExercise, setCurrentDate, syncCheckin, toggleExerciseCompleted } from '@/store/checkinSlice';
+import { getDailyCheckins, loadMonthCheckins, removeExercise, setCurrentDate, syncCheckin, toggleExerciseCompleted } from '@/store/checkinSlice';
 import { Ionicons } from '@expo/vector-icons';
 import { useFocusEffect } from '@react-navigation/native';
 import { useRouter } from 'expo-router';
@@ -32,6 +32,9 @@ export default function CheckinHome() {
     dispatch(getDailyCheckins(today)).unwrap().catch((err: any) => {
       Alert.alert('获取打卡失败', err?.message || '请稍后重试');
     });
+    // 预取本月数据（用于日历视图点亮）
+    const now = new Date();
+    dispatch(loadMonthCheckins({ year: now.getFullYear(), month1Based: now.getMonth() + 1 }));
   }, [dispatch, today]);
 
   useFocusEffect(
@@ -52,7 +55,7 @@ export default function CheckinHome() {
           <View style={[styles.blob, { backgroundColor: colorTokens.ornamentAccent, bottom: -70, left: -70 }]} />
         </View>
 
-        <HeaderBar title="今日打卡" onBack={() => router.back()} withSafeTop={false} transparent />
+        <HeaderBar title="每日打卡" onBack={() => router.back()} withSafeTop={false} transparent />
         <View style={[styles.hero, { backgroundColor: colorTokens.heroSurfaceTint }]}>
           <Text style={[styles.title, { color: colorTokens.text }]}>{today}</Text>
           <Text style={[styles.subtitle, { color: colorTokens.textMuted }]}>请选择动作并记录完成情况</Text>