feat(fasting): 新增轻断食功能模块

新增完整的轻断食功能，包括：
- 断食计划列表和详情页面，支持12-12、14-10、16-8、18-6四种计划
- 断食状态实时追踪和倒计时显示
- 自定义开始时间选择器
- 断食通知提醒功能
- Redux状态管理和数据持久化
- 新增tab导航入口和路由配置

utils/fasting.ts

@@ -0,0 +1,191 @@
+import dayjs from 'dayjs';
+import duration from 'dayjs/plugin/duration';
+import isSameOrAfter from 'dayjs/plugin/isSameOrAfter';
+import isSameOrBefore from 'dayjs/plugin/isSameOrBefore';
+import AsyncStorage from '@/utils/kvStore';
+import { FASTING_STORAGE_KEYS } from '@/constants/Fasting';
+
+dayjs.extend(duration);
+dayjs.extend(isSameOrAfter);
+dayjs.extend(isSameOrBefore);
+
+export type FastingPhase = 'upcoming' | 'fasting' | 'completed';
+
+export const calculateFastingWindow = (start: Date, fastingHours: number) => {
+  const startDate = dayjs(start).second(0).millisecond(0);
+  const endDate = startDate.add(fastingHours, 'hour');
+
+  return {
+    start: startDate.toDate(),
+    end: endDate.toDate(),
+  };
+};
+
+export const getFastingPhase = (start?: Date | null, end?: Date | null, now: Date = new Date()): FastingPhase => {
+  if (!start || !end) {
+    return 'completed';
+  }
+
+  const nowJs = dayjs(now);
+  const startJs = dayjs(start);
+  const endJs = dayjs(end);
+
+  if (nowJs.isBefore(startJs)) {
+    return 'upcoming';
+  }
+  if (nowJs.isSameOrAfter(startJs) && nowJs.isBefore(endJs)) {
+    return 'fasting';
+  }
+  return 'completed';
+};
+
+export const getPhaseLabel = (phase: FastingPhase) => {
+  switch (phase) {
+    case 'fasting':
+      return '断食中';
+    case 'upcoming':
+      return '可饮食';
+    case 'completed':
+      return '可饮食';
+    default:
+      return '可饮食';
+  }
+};
+
+export const formatDayDescriptor = (date: Date | null | undefined, now: Date = new Date()) => {
+  if (!date) return '--';
+
+  const target = dayjs(date);
+  const today = dayjs(now).startOf('day');
+
+  if (target.isSame(today, 'day')) {
+    return '今天';
+  }
+  if (target.isSame(today.subtract(1, 'day'), 'day')) {
+    return '昨天';
+  }
+  if (target.isSame(today.add(1, 'day'), 'day')) {
+    return '明天';
+  }
+  return target.format('MM-DD');
+};
+
+export const formatTime = (date: Date | null | undefined) => {
+  if (!date) return '--:--';
+  return dayjs(date).format('HH:mm');
+};
+
+export const formatCountdown = (target: Date | null | undefined, now: Date = new Date()) => {
+  if (!target) return '--:--:--';
+
+  const diff = dayjs(target).diff(now);
+  if (diff <= 0) {
+    return '00:00:00';
+  }
+
+  const dur = dayjs.duration(diff);
+  const hours = String(Math.floor(dur.asHours())).padStart(2, '0');
+  const minutes = String(dur.minutes()).padStart(2, '0');
+  const seconds = String(dur.seconds()).padStart(2, '0');
+
+  return `${hours}:${minutes}:${seconds}`;
+};
+
+export const buildDisplayWindow = (start?: Date | null, end?: Date | null) => {
+  return {
+    startDayLabel: formatDayDescriptor(start ?? null),
+    startTimeLabel: formatTime(start ?? null),
+    endDayLabel: formatDayDescriptor(end ?? null),
+    endTimeLabel: formatTime(end ?? null),
+  };
+};
+
+export const loadPreferredPlanId = async (): Promise<string | null> => {
+  try {
+    return await AsyncStorage.getItem(FASTING_STORAGE_KEYS.preferredPlanId);
+  } catch (error) {
+    console.warn('加载断食首选计划ID失败', error);
+    return null;
+  }
+};
+
+export const savePreferredPlanId = async (planId: string) => {
+  try {
+    await AsyncStorage.setItem(FASTING_STORAGE_KEYS.preferredPlanId, planId);
+  } catch (error) {
+    console.warn('保存断食首选计划ID失败', error);
+  }
+};
+
+export type FastingNotificationIds = {
+  startId?: string | null;
+  endId?: string | null;
+};
+
+export const getFastingNotificationsRegistered = async (): Promise<boolean> => {
+  try {
+    const value = await AsyncStorage.getItem(FASTING_STORAGE_KEYS.notificationsRegistered);
+    return value === 'true';
+  } catch (error) {
+    console.warn('读取断食通知注册状态失败', error);
+    return false;
+  }
+};
+
+export const setFastingNotificationsRegistered = async (registered: boolean) => {
+  try {
+    if (registered) {
+      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.notificationsRegistered, 'true');
+    } else {
+      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.notificationsRegistered);
+    }
+  } catch (error) {
+    console.warn('更新断食通知注册状态失败', error);
+  }
+};
+
+export const loadStoredFastingNotificationIds = async (): Promise<FastingNotificationIds> => {
+  try {
+    const [startId, endId] = await Promise.all([
+      AsyncStorage.getItem(FASTING_STORAGE_KEYS.startNotificationId),
+      AsyncStorage.getItem(FASTING_STORAGE_KEYS.endNotificationId),
+    ]);
+
+    return {
+      startId: startId ?? undefined,
+      endId: endId ?? undefined,
+    };
+  } catch (error) {
+    console.warn('读取断食通知ID失败', error);
+    return {};
+  }
+};
+
+export const saveFastingNotificationIds = async (ids: FastingNotificationIds) => {
+  try {
+    if (ids.startId) {
+      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.startNotificationId, ids.startId);
+    } else {
+      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId);
+    }
+
+    if (ids.endId) {
+      await AsyncStorage.setItem(FASTING_STORAGE_KEYS.endNotificationId, ids.endId);
+    } else {
+      await AsyncStorage.removeItem(FASTING_STORAGE_KEYS.endNotificationId);
+    }
+  } catch (error) {
+    console.warn('保存断食通知ID失败', error);
+  }
+};
+
+export const clearFastingNotificationIds = async () => {
+  try {
+    await Promise.all([
+      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.startNotificationId),
+      AsyncStorage.removeItem(FASTING_STORAGE_KEYS.endNotificationId),
+    ]);
+  } catch (error) {
+    console.warn('清除断食通知ID失败', error);
+  }
+};