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/(tabs)/explore.tsx

@@ -10,6 +10,7 @@ import { ensureHealthPermissions, fetchHealthDataForDate, fetchTodayHealthData }
 import { Ionicons } from '@expo/vector-icons';
 import { useBottomTabBarHeight } from '@react-navigation/bottom-tabs';
 import { useFocusEffect } from '@react-navigation/native';
+import { useRouter } from 'expo-router';
 import React, { useEffect, useMemo, useRef, useState } from 'react';
 import {
   SafeAreaView,
@@ -22,6 +23,7 @@ import {
 import { useSafeAreaInsets } from 'react-native-safe-area-context';
 
 export default function ExploreScreen() {
+  const router = useRouter();
   const theme = (useColorScheme() ?? 'light') as 'light' | 'dark';
   const colorTokens = Colors[theme];
   const stepGoal = useAppSelector((s) => s.user.profile?.dailyStepsGoal) ?? 2000;
@@ -143,8 +145,13 @@ export default function ExploreScreen() {
             })}
           </ScrollView>
 
-          {/* 今日报告 标题 */}
-          <Text style={styles.sectionTitle}>今日报告</Text>
+          {/* 打卡入口 */}
+          <View style={{ flexDirection: 'row', justifyContent: 'space-between', alignItems: 'center', marginTop: 24, marginBottom: 8 }}>
+            <Text style={styles.sectionTitle}>今日报告</Text>
+            <TouchableOpacity onPress={() => router.push('/checkin/calendar')} accessibilityRole="button">
+              <Text style={{ color: '#6B7280', fontWeight: '700' }}>查看打卡日历</Text>
+            </TouchableOpacity>
+          </View>
 
           {/* 取消卡片内 loading，保持静默刷新提升体验 */}