feat(medications): 添加药品结束日期选择功能

- 新增药品结束日期选择器，支持设置服药周期
- 优化日期显示格式，从"开始日期"改为"服药周期"
- 添加日期验证逻辑，确保开始日期不早于今天且结束日期不早于开始日期
- 改进添加药品页面的日期选择UI，采用并排布局
- 调整InfoCard组件样式，移除图标背景色并减小字体大小

app/medications/add-medication.tsx

@@ -128,7 +128,7 @@ export default function AddMedicationScreen() {
   const { upload, uploading } = useCosUpload({ prefix: 'images/medications' });
   // 获取登录验证相关的功能
   const { ensureLoggedIn } = useAuthGuard();
-  const softBorderColor = useMemo(() => withAlpha(colors.border, 0.45), [colors.border]);
+  const softBorderColor = useMemo(() => withAlpha(colors.border, 0.25), [colors.border]);
   const fadedBorderFill = useMemo(() => withAlpha('#ffffff', 1), [colors.border]);
   const glassPrimaryTint = useMemo(() => withAlpha(colors.primary, theme === 'dark' ? 0.55 : 0.45), [colors.primary, theme]);
   const glassDisabledTint = useMemo(() => withAlpha(colors.border, theme === 'dark' ? 0.45 : 0.6), [colors.border, theme]);
@@ -146,8 +146,12 @@ export default function AddMedicationScreen() {
   const [timesPickerVisible, setTimesPickerVisible] = useState(false);
   const [timesPickerValue, setTimesPickerValue] = useState(1);
   const [startDate, setStartDate] = useState<Date>(new Date());
+  const [endDate, setEndDate] = useState<Date | null>(null);
   const [datePickerVisible, setDatePickerVisible] = useState(false);
   const [datePickerValue, setDatePickerValue] = useState<Date>(new Date());
+  const [endDatePickerVisible, setEndDatePickerVisible] = useState(false);
+  const [endDatePickerValue, setEndDatePickerValue] = useState<Date>(new Date());
+  const [datePickerMode, setDatePickerMode] = useState<'start' | 'end'>('start');
   const [medicationTimes, setMedicationTimes] = useState<string[]>([DEFAULT_TIME_PRESETS[0]]);
   const [timePickerVisible, setTimePickerVisible] = useState(false);
   const [timePickerDate, setTimePickerDate] = useState<Date>(createDateFromTime(DEFAULT_TIME_PRESETS[0]));
@@ -276,6 +280,7 @@ export default function AddMedicationScreen() {
         timesPerDay: timesPerDay,
         medicationTimes: medicationTimes,
         startDate: dayjs(startDate).startOf('day').toISOString(), // ISO 8601 格式
+        endDate: endDate ? dayjs(endDate).endOf('day').toISOString() : undefined, // 如果有结束日期，设置为当天结束时间
         repeatPattern: 'daily' as RepeatPattern,
         note: note.trim() || undefined,
       };
@@ -332,6 +337,7 @@ export default function AddMedicationScreen() {
     dosageUnit,
     medicationTimes,
     startDate,
+    endDate,
     note,
     dispatch,
     ensureLoggedIn,
@@ -469,15 +475,47 @@ export default function AddMedicationScreen() {
     setPhotoUrl(null);
   }, []);
 
-  const openDatePicker = useCallback(() => {
+  const openStartDatePicker = useCallback(() => {
     setDatePickerValue(startDate);
     setDatePickerVisible(true);
   }, [startDate]);
 
+  const openEndDatePicker = useCallback(() => {
+    setEndDatePickerValue(endDate || new Date());
+    setEndDatePickerVisible(true);
+  }, [endDate]);
+
   const confirmStartDate = useCallback((date: Date) => {
+    // 验证开始日期不能早于今天
+    const today = new Date();
+    today.setHours(0, 0, 0, 0);
+    const selectedDate = new Date(date);
+    selectedDate.setHours(0, 0, 0, 0);
+    
+    if (selectedDate < today) {
+      Alert.alert('日期无效', '开始日期不能早于今天');
+      return;
+    }
+    
     setStartDate(date);
     setDatePickerVisible(false);
-  }, []);
+    
+    // 如果结束日期早于新的开始日期，清空结束日期
+    if (endDate && endDate < date) {
+      setEndDate(null);
+    }
+  }, [endDate]);
+
+  const confirmEndDate = useCallback((date: Date) => {
+    // 验证结束日期不能早于开始日期
+    if (date < startDate) {
+      Alert.alert('日期无效', '结束日期不能早于开始日期');
+      return;
+    }
+    
+    setEndDate(date);
+    setEndDatePickerVisible(false);
+  }, [startDate]);
 
   const openTimePicker = useCallback(
     (index?: number) => {
@@ -718,7 +756,6 @@ export default function AddMedicationScreen() {
       case 2:
         return (
           <View style={styles.stepSection}>
-
             <View style={styles.inputGroup}>
               <ThemedText style={[styles.groupLabel, { color: colors.textSecondary }]}>每日次数</ThemedText>
               <TouchableOpacity
@@ -736,6 +773,57 @@ export default function AddMedicationScreen() {
                 <Ionicons name="chevron-down" size={18} color={colors.textSecondary} />
               </TouchableOpacity>
             </View>
+
+            <View style={styles.inputGroup}>
+              <View style={styles.periodHeader}>
+                <ThemedText style={[styles.groupLabel, { color: colors.textSecondary }]}>用药周期</ThemedText>
+              </View>
+              <View style={styles.dateRowContainer}>
+                <TouchableOpacity
+                  activeOpacity={0.85}
+                  style={[
+                    styles.dateRow,
+                    styles.dateRowHalf,
+                    {
+                      borderColor: softBorderColor,
+                      backgroundColor: colors.surface,
+                    },
+                  ]}
+                  onPress={openStartDatePicker}
+                >
+                  <View style={styles.dateLeft}>
+                    <Ionicons name="calendar" size={16} color={colors.textSecondary} />
+                    <ThemedText style={[styles.dateLabel, { color: colors.textMuted }]}>开始</ThemedText>
+                    <ThemedText style={[styles.dateValue, { color: colors.text }]}>
+                      {dayjs(startDate).format('MM/DD')}
+                    </ThemedText>
+                  </View>
+                  <Ionicons name="chevron-forward" size={16} color={colors.textSecondary} />
+                </TouchableOpacity>
+                
+                <TouchableOpacity
+                  activeOpacity={0.85}
+                  style={[
+                    styles.dateRow,
+                    styles.dateRowHalf,
+                    {
+                      borderColor: softBorderColor,
+                      backgroundColor: colors.surface,
+                    },
+                  ]}
+                  onPress={openEndDatePicker}
+                >
+                  <View style={styles.dateLeft}>
+                    <Ionicons name="calendar-outline" size={16} color={colors.textSecondary} />
+                    <ThemedText style={[styles.dateLabel, { color: colors.textMuted }]}>结束</ThemedText>
+                    <ThemedText style={[styles.dateValue, { color: colors.text }]}>
+                      {endDate ? dayjs(endDate).format('MM/DD') : '长期'}
+                    </ThemedText>
+                  </View>
+                  <Ionicons name="chevron-forward" size={16} color={colors.textSecondary} />
+                </TouchableOpacity>
+              </View>
+            </View>
           </View>
         );
       case 3:
@@ -895,30 +983,6 @@ export default function AddMedicationScreen() {
             <View style={styles.contentContainer}>{renderStepContent()}</View>
 
             <View style={styles.footer}>
-              {showDateField && (
-                <TouchableOpacity
-                  activeOpacity={0.85}
-                  style={[
-                    styles.startDateRow,
-                    {
-                      borderColor: softBorderColor,
-                      backgroundColor: colors.surface,
-                    },
-                  ]}
-                  onPress={openDatePicker}
-                >
-                  <View style={styles.startDateLeft}>
-                    <Ionicons name="calendar" size={18} color={colors.textSecondary} />
-                    <View>
-                      <ThemedText style={[styles.startDateLabel, { color: colors.textMuted }]}>开始日期</ThemedText>
-                      <ThemedText style={[styles.startDateValue, { color: colors.text }]}>
-                        {dayjs(startDate).format('YYYY 年 MM 月 DD 日')}
-                      </ThemedText>
-                    </View>
-                  </View>
-                  <Ionicons name="chevron-forward" size={18} color={colors.textSecondary} />
-                </TouchableOpacity>
-              )}
 
               <View style={styles.footerButtons}>
                 {currentStep > 0 && (
@@ -1010,6 +1074,7 @@ export default function AddMedicationScreen() {
         <Pressable style={styles.pickerBackdrop} onPress={() => setDatePickerVisible(false)} />
         <View style={[styles.pickerSheet, { backgroundColor: colors.surface }]}
         >
+          <ThemedText style={[styles.modalTitle, { color: colors.text }]}>选择开始日期</ThemedText>
           <DateTimePicker
             value={datePickerValue}
             mode="date"
@@ -1045,6 +1110,51 @@ export default function AddMedicationScreen() {
         </View>
       </Modal>
 
+      <Modal
+        visible={endDatePickerVisible}
+        transparent
+        animationType="fade"
+        onRequestClose={() => setEndDatePickerVisible(false)}
+      >
+        <Pressable style={styles.pickerBackdrop} onPress={() => setEndDatePickerVisible(false)} />
+        <View style={[styles.pickerSheet, { backgroundColor: colors.surface }]}
+        >
+          <ThemedText style={[styles.modalTitle, { color: colors.text }]}>选择结束日期</ThemedText>
+          <DateTimePicker
+            value={endDatePickerValue}
+            mode="date"
+            display={Platform.OS === 'ios' ? 'inline' : 'calendar'}
+            onChange={(event, date) => {
+              if (Platform.OS === 'ios') {
+                if (date) setEndDatePickerValue(date);
+              } else {
+                if (event.type === 'set' && date) {
+                  confirmEndDate(date);
+                } else {
+                  setEndDatePickerVisible(false);
+                }
+              }
+            }}
+          />
+          {Platform.OS === 'ios' && (
+            <View style={styles.modalActions}>
+              <Pressable
+                onPress={() => setEndDatePickerVisible(false)}
+                style={[styles.modalBtn, { borderColor: softBorderColor }]}
+              >
+                <ThemedText style={[styles.modalBtnText, { color: colors.textSecondary }]}>取消</ThemedText>
+              </Pressable>
+              <Pressable
+                onPress={() => confirmEndDate(endDatePickerValue)}
+                style={[styles.modalBtn, styles.modalBtnPrimary, { backgroundColor: colors.primary }]}
+              >
+                <ThemedText style={[styles.modalBtnText, { color: colors.onPrimary }]}>确定</ThemedText>
+              </Pressable>
+            </View>
+          )}
+        </View>
+      </Modal>
+
       <Modal
         visible={timePickerVisible}
         transparent
@@ -1500,6 +1610,39 @@ const styles = StyleSheet.create({
   footer: {
     gap: 12,
   },
+  periodHeader: {
+    flexDirection: 'row',
+    justifyContent: 'space-between',
+    alignItems: 'center',
+  },
+  dateRowContainer: {
+    flexDirection: 'row',
+    gap: 12,
+  },
+  dateRow: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    justifyContent: 'space-between',
+    borderWidth: 1,
+    borderRadius: 18,
+    paddingHorizontal: 12,
+    paddingVertical: 10,
+  },
+  dateRowHalf: {
+    flex: 1,
+  },
+  dateLeft: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    gap: 8,
+  },
+  dateLabel: {
+    fontSize: 11,
+  },
+  dateValue: {
+    fontSize: 14,
+    fontWeight: '600',
+  },
   startDateRow: {
     flexDirection: 'row',
     alignItems: 'center',