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

components/fasting/FastingStartPickerModal.tsx

@@ -0,0 +1,242 @@
+import React, { useEffect, useMemo, useRef, useState } from 'react';
+import { StyleSheet, Text, TouchableOpacity, View } from 'react-native';
+import WheelPickerExpo from 'react-native-wheel-picker-expo';
+import dayjs from 'dayjs';
+import { FloatingSelectionCard } from '@/components/ui/FloatingSelectionCard';
+import { Colors } from '@/constants/Colors';
+import { useColorScheme } from '@/hooks/useColorScheme';
+
+type FastingStartPickerModalProps = {
+  visible: boolean;
+  onClose: () => void;
+  initialDate?: Date | null;
+  recommendedDate?: Date | null;
+  onConfirm: (date: Date) => void;
+};
+
+type DayOption = {
+  label: string;
+  offset: number;
+};
+
+const buildDayOptions = (now: dayjs.Dayjs): DayOption[] => ([
+  { offset: -1, label: '昨天' },
+  { offset: 0, label: '今天' },
+  { offset: 1, label: '明天' },
+].map((item) => ({
+  ...item,
+  label: item.offset === -1
+    ? '昨天'
+    : item.offset === 0
+      ? '今天'
+      : '明天',
+})));
+
+const HOURS = Array.from({ length: 24 }, (_, i) => i);
+const MINUTES = Array.from({ length: 12 }, (_, i) => i * 5);
+
+export function FastingStartPickerModal({
+  visible,
+  onClose,
+  initialDate,
+  recommendedDate,
+  onConfirm,
+}: FastingStartPickerModalProps) {
+  const theme = useColorScheme() ?? 'light';
+  const colors = Colors[theme];
+  const now = useMemo(() => dayjs(), []);
+  const dayOptions = useMemo(() => buildDayOptions(now), [now]);
+
+  const deriveInitialIndexes = (source?: Date | null) => {
+    const seed = source ? dayjs(source) : now;
+    const dayDiff = seed.startOf('day').diff(now.startOf('day'), 'day');
+    const dayIndex = dayOptions.findIndex((option) => option.offset === dayDiff);
+    const hourIndex = HOURS.findIndex((hour) => hour === seed.hour());
+    const snappedMinute = seed.minute() - (seed.minute() % 5);
+    const minuteIndex = MINUTES.findIndex((minute) => minute === snappedMinute);
+
+    return {
+      dayIndex: dayIndex === -1 ? 1 : dayIndex,
+      hourIndex: hourIndex === -1 ? now.hour() : hourIndex,
+      minuteIndex:
+        minuteIndex === -1
+          ? Math.max(0, Math.min(MINUTES.length - 1, Math.floor(seed.minute() / 5)))
+          : minuteIndex,
+    };
+  };
+
+  const defaultBaseRef = useRef(new Date());
+
+  const baseDate = useMemo(
+    () => initialDate ?? recommendedDate ?? defaultBaseRef.current,
+    [initialDate, recommendedDate]
+  );
+
+  const baseTimestamp = baseDate.getTime();
+
+  const [{ dayIndex, hourIndex, minuteIndex }, setIndexes] = useState(() =>
+    deriveInitialIndexes(baseDate)
+  );
+  const [pickerKey, setPickerKey] = useState(0);
+  const lastAppliedTimestamp = useRef<number | null>(null);
+  const wasVisibleRef = useRef(false);
+
+  useEffect(() => {
+    if (!visible) {
+      wasVisibleRef.current = false;
+      return;
+    }
+
+    const shouldReset =
+      !wasVisibleRef.current ||
+      lastAppliedTimestamp.current !== baseTimestamp;
+
+    if (shouldReset) {
+      const nextIndexes = deriveInitialIndexes(baseDate);
+      setIndexes(nextIndexes);
+      setPickerKey((prev) => prev + 1);
+      lastAppliedTimestamp.current = baseTimestamp;
+    }
+
+    wasVisibleRef.current = true;
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [visible, baseTimestamp]);
+
+  const handleConfirm = () => {
+    const selectedDay = dayOptions[dayIndex] ?? dayOptions[1];
+    const base = now.startOf('day').add(selectedDay?.offset ?? 0, 'day');
+    const hour = HOURS[hourIndex] ?? now.hour();
+    const minute = MINUTES[minuteIndex] ?? 0;
+    const result = base.hour(hour).minute(minute).second(0).millisecond(0);
+    onConfirm(result.toDate());
+    onClose();
+  };
+
+  const handleUseRecommended = () => {
+    if (!recommendedDate) return;
+    setIndexes(deriveInitialIndexes(recommendedDate));
+    setPickerKey((prev) => prev + 1);
+    lastAppliedTimestamp.current = recommendedDate.getTime();
+  };
+
+  const pickerIndicatorStyle = useMemo(
+    () => ({
+      backgroundColor: `${colors.primary}12`,
+      borderRadius: 12,
+    }),
+    [colors.primary]
+  );
+
+  const textStyle = {
+    fontSize: 18,
+    fontWeight: '600' as const,
+    color: '#2E3142',
+  };
+
+  return (
+    <FloatingSelectionCard
+      visible={visible}
+      onClose={onClose}
+      title="断食开始时间"
+    >
+      <View style={styles.pickerRow}>
+        <WheelPickerExpo
+          key={`day-${pickerKey}`}
+          height={180}
+          width={110}
+          initialSelectedIndex={dayIndex}
+          items={dayOptions.map((item) => ({ label: item.label, value: item.offset }))}
+          onChange={({ index }) => setIndexes((prev) => ({ ...prev, dayIndex: index }))}
+          backgroundColor="transparent"
+          itemTextStyle={textStyle}
+          selectedIndicatorStyle={pickerIndicatorStyle}
+          haptics
+        />
+        <WheelPickerExpo
+          key={`hour-${pickerKey}`}
+          height={180}
+          width={110}
+          initialSelectedIndex={hourIndex}
+          items={HOURS.map((hour) => ({ label: hour.toString().padStart(2, '0'), value: hour }))}
+          onChange={({ index }) => setIndexes((prev) => ({ ...prev, hourIndex: index }))}
+          backgroundColor="transparent"
+          itemTextStyle={textStyle}
+          selectedIndicatorStyle={pickerIndicatorStyle}
+          haptics
+        />
+        <WheelPickerExpo
+          key={`minute-${pickerKey}`}
+          height={180}
+          width={110}
+          initialSelectedIndex={minuteIndex}
+          items={MINUTES.map((minute) => ({
+            label: minute.toString().padStart(2, '0'),
+            value: minute,
+          }))}
+          onChange={({ index }) => setIndexes((prev) => ({ ...prev, minuteIndex: index }))}
+          backgroundColor="transparent"
+          itemTextStyle={textStyle}
+          selectedIndicatorStyle={pickerIndicatorStyle}
+          haptics
+        />
+      </View>
+
+      <View style={styles.footerRow}>
+        <TouchableOpacity
+          style={[styles.recommendButton, { borderColor: colors.primary }]}
+          onPress={handleUseRecommended}
+          activeOpacity={0.85}
+        >
+          <Text style={[styles.recommendButtonText, { color: colors.primary }]}>使用推荐时间</Text>
+        </TouchableOpacity>
+        <TouchableOpacity
+          style={[styles.confirmButton, { backgroundColor: colors.primary }]}
+          onPress={handleConfirm}
+          activeOpacity={0.9}
+        >
+          <Text style={styles.confirmButtonText}>确定</Text>
+        </TouchableOpacity>
+      </View>
+    </FloatingSelectionCard>
+  );
+}
+
+const styles = StyleSheet.create({
+  pickerRow: {
+    flexDirection: 'row',
+    justifyContent: 'space-between',
+    width: '100%',
+    marginBottom: 24,
+  },
+  footerRow: {
+    flexDirection: 'row',
+    justifyContent: 'space-between',
+    width: '100%',
+  },
+  recommendButton: {
+    flex: 1,
+    borderWidth: 1.2,
+    borderRadius: 24,
+    paddingVertical: 12,
+    marginRight: 12,
+    alignItems: 'center',
+    justifyContent: 'center',
+    backgroundColor: 'rgba(255,255,255,0.95)',
+  },
+  recommendButtonText: {
+    fontSize: 14,
+    fontWeight: '600',
+  },
+  confirmButton: {
+    flex: 1,
+    borderRadius: 24,
+    paddingVertical: 12,
+    alignItems: 'center',
+    justifyContent: 'center',
+  },
+  confirmButtonText: {
+    fontSize: 15,
+    fontWeight: '700',
+    color: '#fff',
+  },
+});