fix(ios): 修复HealthKit类型安全性并优化HRV通知频率

将HealthKit数据类型从强制解包改为可选类型，避免潜在的运行时崩溃。所有数据类型访问现在都通过guard语句进行安全检查，当类型不可用时返回明确的错误信息。同时修复了活动摘要日期计算错误，确保每个摘要使用正确的日期。

HRV压力通知的最小间隔从4小时缩短至2小时，并移除了每日一次的限制，允许更及时的压力状态提醒。

BREAKING CHANGE: HealthKit数据类型API现在可能返回"TYPE_NOT_AVAILABLE"错误，调用方需要处理此新错误类型

services/hrvMonitor.ts

@@ -1,16 +1,15 @@
-import { logger } from '@/utils/logger';
-import AsyncStorage from '@/utils/kvStore';
-import dayjs from 'dayjs';
-import { NativeEventEmitter, NativeModules } from 'react-native';
 import { analyzeHRVData, fetchHRVWithStatus } from '@/utils/health';
+import AsyncStorage from '@/utils/kvStore';
+import { logger } from '@/utils/logger';
 import { convertHrvToStressIndex, getStressLevelInfo, StressLevel } from '@/utils/stress';
+import { NativeEventEmitter, NativeModules } from 'react-native';
 import { sendHRVStressNotification } from './hrvNotificationService';
 
 const { HealthKitManager } = NativeModules;
 
 const HRV_EVENT_NAME = 'hrvUpdate';
 const HRV_NOTIFICATION_STATE_KEY = '@hrv_stress_notification_state';
-const MIN_NOTIFICATION_INTERVAL_HOURS = 4;
+const MIN_NOTIFICATION_INTERVAL_HOURS = 2;
 
 interface HrvEventData {
   timestamp: number;
@@ -137,19 +136,13 @@ class HRVMonitorService {
       const elapsed = now - state.lastSentAt;
       const minIntervalMs = MIN_NOTIFICATION_INTERVAL_HOURS * 60 * 60 * 1000;
 
+      // 只检查最小间隔时间（2小时），不再限制每天只能发送一次
       if (elapsed < minIntervalMs) {
         const hoursLeft = ((minIntervalMs - elapsed) / (1000 * 60 * 60)).toFixed(1);
         logger.info(`[HRVMonitor] Cooldown active, ${hoursLeft}h remaining`);
         return false;
       }
 
-      const lastSentDay = dayjs(state.lastSentAt).format('YYYY-MM-DD');
-      const today = dayjs().format('YYYY-MM-DD');
-      if (lastSentDay === today && state.lastStressLevel !== 'high') {
-        logger.info('[HRVMonitor] Already sent HRV notification today');
-        return false;
-      }
-
       return true;
     } catch (error) {
       logger.warn('[HRVMonitor] Failed to read notification state:', error);