feat(fasting): 添加周期性断食计划功能

实现完整的周期性断食计划系统，支持每日自动续订和通知管理：

- 新增周期性断食状态管理（activeCycle、currentCycleSession、cycleHistory）
- 实现周期性断食会话的自动完成和续订逻辑
- 添加独立的周期性断食通知系统，避免与单次断食通知冲突
- 支持暂停/恢复周期性断食计划
- 添加周期性断食数据持久化和水合功能
- 优化断食界面，优先显示周期性断食信息
- 新增空状态引导界面，提升用户体验
- 保持单次断食功能向后兼容

utils/fasting.ts

@@ -255,3 +255,153 @@ export const clearFastingNotificationIds = async () => {
     console.warn('清除断食通知ID失败', error);
   }
 };
+
+// 周期性断食相关的存储函数
+export const loadActiveFastingCycle = async (): Promise<any | null> => {
+  try {
+    const stored = await AsyncStorage.getItem('@fasting_active_cycle');
+    if (!stored) return null;
+    
+    const parsed = JSON.parse(stored);
+    return parsed;
+  } catch (error) {
+    console.warn('读取周期性断食计划失败', error);
+    return null;
+  }
+};
+
+export const saveActiveFastingCycle = async (cycle: any | null): Promise<void> => {
+  try {
+    if (cycle) {
+      await AsyncStorage.setItem('@fasting_active_cycle', JSON.stringify(cycle));
+    } else {
+      await AsyncStorage.removeItem('@fasting_active_cycle');
+    }
+  } catch (error) {
+    console.error('保存周期性断食计划失败', error);
+    throw new Error('保存周期性断食计划失败，请稍后重试');
+  }
+};
+
+export const loadCurrentCycleSession = async (): Promise<any | null> => {
+  try {
+    const stored = await AsyncStorage.getItem('@fasting_current_cycle_session');
+    if (!stored) return null;
+    
+    const parsed = JSON.parse(stored);
+    return parsed;
+  } catch (error) {
+    console.warn('读取当前断食会话失败', error);
+    return null;
+  }
+};
+
+export const saveCurrentCycleSession = async (session: any | null): Promise<void> => {
+  try {
+    if (session) {
+      await AsyncStorage.setItem('@fasting_current_cycle_session', JSON.stringify(session));
+    } else {
+      await AsyncStorage.removeItem('@fasting_current_cycle_session');
+    }
+  } catch (error) {
+    console.error('保存当前断食会话失败', error);
+    throw new Error('保存断食会话失败，请稍后重试');
+  }
+};
+
+export const loadCycleHistory = async (): Promise<any[]> => {
+  try {
+    const stored = await AsyncStorage.getItem('@fasting_cycle_history');
+    if (!stored) return [];
+    
+    const parsed = JSON.parse(stored);
+    return Array.isArray(parsed) ? parsed : [];
+  } catch (error) {
+    console.warn('读取断食周期历史失败', error);
+    return [];
+  }
+};
+
+export const saveCycleHistory = async (history: any[]): Promise<void> => {
+  try {
+    await AsyncStorage.setItem('@fasting_cycle_history', JSON.stringify(history));
+  } catch (error) {
+    console.error('保存断食周期历史失败', error);
+    throw new Error('保存断食历史失败，请稍后重试');
+  }
+};
+
+// 计算下一个断食周期的开始时间
+export const calculateNextCycleStart = (
+  cycle: { startHour: number; startMinute: number },
+  baseDate: Date = new Date()
+): Date => {
+  const now = dayjs(baseDate);
+  const today = now.startOf('day').hour(cycle.startHour).minute(cycle.startMinute).second(0).millisecond(0);
+  
+  // 如果今天的开始时间已过，则从明天开始
+  if (today.isBefore(now)) {
+    return today.add(1, 'day').toDate();
+  }
+  
+  return today.toDate();
+};
+
+// 获取周期性断食的统计信息
+export const getCycleStats = (history: any[]) => {
+  const completedCycles = history.filter(session => session.completed);
+  const totalCycles = history.length;
+  const currentStreak = calculateCurrentStreak(history);
+  const longestStreak = calculateLongestStreak(history);
+  
+  return {
+    totalCycles,
+    completedCycles: completedCycles.length,
+    completionRate: totalCycles > 0 ? (completedCycles.length / totalCycles) * 100 : 0,
+    currentStreak,
+    longestStreak,
+  };
+};
+
+// 计算当前连续完成天数
+const calculateCurrentStreak = (history: any[]): number => {
+  if (history.length === 0) return 0;
+  
+  let streak = 0;
+  const today = dayjs().startOf('day');
+  
+  for (let i = 0; i < history.length; i++) {
+    const session = history[i];
+    if (!session.completed) break;
+    
+    const sessionDate = dayjs(session.cycleDate);
+    const expectedDate = today.subtract(i, 'day');
+    
+    if (sessionDate.isSame(expectedDate, 'day')) {
+      streak++;
+    } else {
+      break;
+    }
+  }
+  
+  return streak;
+};
+
+// 计算最长连续完成天数
+const calculateLongestStreak = (history: any[]): number => {
+  if (history.length === 0) return 0;
+  
+  let longestStreak = 0;
+  let currentStreak = 0;
+  
+  for (const session of history) {
+    if (session.completed) {
+      currentStreak++;
+      longestStreak = Math.max(longestStreak, currentStreak);
+    } else {
+      currentStreak = 0;
+    }
+  }
+  
+  return longestStreak;
+};