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

services/aiCoachSession.ts

@@ -0,0 +1,46 @@
+import AsyncStorage from '@react-native-async-storage/async-storage';
+
+export type AiCoachChatMessage = {
+  id: string;
+  role: 'user' | 'assistant';
+  content: string;
+};
+
+export type AiCoachSessionCache = {
+  conversationId?: string;
+  messages: AiCoachChatMessage[];
+  updatedAt: number;
+};
+
+const STORAGE_KEY = '@ai_coach_session_v1';
+
+export async function loadAiCoachSessionCache(): Promise<AiCoachSessionCache | null> {
+  try {
+    const s = await AsyncStorage.getItem(STORAGE_KEY);
+    if (!s) return null;
+    const obj = JSON.parse(s) as AiCoachSessionCache;
+    if (!obj || !Array.isArray(obj.messages)) return null;
+    return obj;
+  } catch {
+    return null;
+  }
+}
+
+export async function saveAiCoachSessionCache(cache: AiCoachSessionCache): Promise<void> {
+  try {
+    const payload: AiCoachSessionCache = {
+      conversationId: cache.conversationId,
+      messages: cache.messages?.slice?.(-200) ?? [], // 限制最多缓存 200 条，避免无限增长
+      updatedAt: Date.now(),
+    };
+    await AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(payload));
+  } catch { }
+}
+
+export async function clearAiCoachSessionCache(): Promise<void> {
+  try {
+    await AsyncStorage.removeItem(STORAGE_KEY);
+  } catch { }
+}
+
+