feat: 实现减脂体重管理App完整功能

- 实现拍照识别食物功能（集成大语言模型视觉能力）
- 实现智能对话功能（集成大语言模型流式输出）
- 实现食物记录和卡路里管理功能
- 实现体重记录和统计功能
- 实现健康数据管理页面
- 配置数据库表结构（用户、食物记录、体重记录）
- 实现Express后端API路由
- 配置Tab导航和前端页面
- 采用健康运动配色方案

client/screens/stats/index.tsx

@@ -0,0 +1,346 @@
+import React, { useState, useEffect, useMemo } from 'react';
+import { View, ScrollView, TouchableOpacity, TextInput, Modal, Alert } from 'react-native';
+import { useTheme } from '@/hooks/useTheme';
+import { Screen } from '@/components/Screen';
+import { ThemedText } from '@/components/ThemedText';
+import { ThemedView } from '@/components/ThemedView';
+import { FontAwesome6 } from '@expo/vector-icons';
+import { createStyles } from './styles';
+
+const MOCK_USER_ID = 'mock-user-001';
+
+interface WeightRecord {
+  id: string;
+  weight: number;
+  note: string;
+  recordedAt: string;
+}
+
+export default function StatsScreen() {
+  const { theme, isDark } = useTheme();
+  const styles = useMemo(() => createStyles(theme), [theme]);
+
+  const [weightRecords, setWeightRecords] = useState<WeightRecord[]>([]);
+  const [modalVisible, setModalVisible] = useState(false);
+  const [newWeight, setNewWeight] = useState('');
+  const [newNote, setNewNote] = useState('');
+  const [loading, setLoading] = useState(false);
+  const [saving, setSaving] = useState(false);
+
+  // 获取体重记录
+  const fetchWeightRecords = async () => {
+    setLoading(true);
+    try {
+      /**
+       * 服务端文件：server/src/routes/weight-records.ts
+       * 接口：GET /api/v1/weight-records
+       * Query 参数：userId: string
+       */
+      const response = await fetch(
+        `${process.env.EXPO_PUBLIC_BACKEND_BASE_URL}/api/v1/weight-records?userId=${MOCK_USER_ID}`
+      );
+      const data = await response.json();
+      if (data.success) {
+        setWeightRecords(data.data);
+      }
+    } catch (error) {
+      console.error('Failed to fetch weight records:', error);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  useEffect(() => {
+    fetchWeightRecords();
+  }, []);
+
+  // 添加体重记录
+  const addWeightRecord = async () => {
+    if (!newWeight) {
+      Alert.alert('提示', '请输入体重');
+      return;
+    }
+
+    setSaving(true);
+    try {
+      const recordData = {
+        userId: MOCK_USER_ID,
+        weight: parseFloat(newWeight),
+        note: newNote,
+        recordedAt: new Date().toISOString(),
+      };
+
+      /**
+       * 服务端文件：server/src/routes/weight-records.ts
+       * 接口：POST /api/v1/weight-records
+       * Body 参数：userId: string, weight: number, note?: string, recordedAt: string
+       */
+      const response = await fetch(
+        `${process.env.EXPO_PUBLIC_BACKEND_BASE_URL}/api/v1/weight-records`,
+        {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify(recordData),
+        }
+      );
+
+      const data = await response.json();
+
+      if (data.success) {
+        Alert.alert('成功', '记录已保存', [
+          { text: '确定', onPress: () => resetModal() },
+        ]);
+        fetchWeightRecords();
+      } else {
+        Alert.alert('失败', data.error || '保存失败，请重试');
+      }
+    } catch (error) {
+      console.error('Save error:', error);
+      Alert.alert('错误', '保存失败，请检查网络连接');
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  const resetModal = () => {
+    setModalVisible(false);
+    setNewWeight('');
+    setNewNote('');
+  };
+
+  // 删除记录
+  const deleteRecord = async (id: string) => {
+    Alert.alert('确认删除', '确定要删除这条记录吗？', [
+      { text: '取消', style: 'cancel' },
+      {
+        text: '删除',
+        style: 'destructive',
+        onPress: async () => {
+          try {
+            /**
+             * 服务端文件：server/src/routes/weight-records.ts
+             * 接口：DELETE /api/v1/weight-records/:id
+             * Path 参数：id: string
+             */
+            const response = await fetch(
+              `${process.env.EXPO_PUBLIC_BACKEND_BASE_URL}/api/v1/weight-records/${id}`,
+              {
+                method: 'DELETE',
+              }
+            );
+            const data = await response.json();
+            if (data.success) {
+              fetchWeightRecords();
+            }
+          } catch (error) {
+            console.error('Delete error:', error);
+          }
+        },
+      },
+    ]);
+  };
+
+  return (
+    <Screen backgroundColor={theme.backgroundRoot} statusBarStyle={isDark ? 'light' : 'dark'}>
+      <ScrollView contentContainerStyle={styles.scrollContent}>
+        <View style={styles.header}>
+          <ThemedText variant="h2" color={theme.textPrimary}>
+            数据统计
+          </ThemedText>
+          <TouchableOpacity
+            style={styles.addButton}
+            onPress={() => setModalVisible(true)}
+          >
+            <FontAwesome6 name="plus" size={18} color={theme.buttonPrimaryText} />
+          </TouchableOpacity>
+        </View>
+
+        {/* 体重趋势 */}
+        <ThemedView level="root" style={styles.chartSection}>
+          <View style={styles.sectionHeader}>
+            <ThemedText variant="h4" color={theme.textPrimary}>
+              体重记录
+            </ThemedText>
+            {weightRecords.length > 0 && (
+              <ThemedText variant="small" color={theme.primary}>
+                {weightRecords.length} 条记录
+              </ThemedText>
+            )}
+          </View>
+
+          {weightRecords.length === 0 ? (
+            <ThemedText variant="small" color={theme.textMuted} style={styles.emptyText}>
+              暂无记录，点击右上角添加
+            </ThemedText>
+          ) : (
+            <View style={styles.recordsList}>
+              {weightRecords.map((record, index) => (
+                <View key={record.id} style={styles.recordItem}>
+                  <View style={styles.recordInfo}>
+                    <View style={styles.recordWeight}>
+                      <ThemedText variant="h3" color={theme.primary}>
+                        {record.weight}
+                      </ThemedText>
+                      <ThemedText variant="small" color={theme.textMuted}>
+                        kg
+                      </ThemedText>
+                    </View>
+                    <View>
+                      <ThemedText variant="small" color={theme.textSecondary}>
+                        {new Date(record.recordedAt).toLocaleDateString('zh-CN', {
+                          month: 'short',
+                          day: 'numeric',
+                        })}
+                      </ThemedText>
+                      {record.note && (
+                        <ThemedText variant="caption" color={theme.textMuted}>
+                          {record.note}
+                        </ThemedText>
+                      )}
+                    </View>
+                  </View>
+
+                  {index > 0 && (
+                    <View style={styles.changeBadge}>
+                      <FontAwesome6
+                        name={record.weight < weightRecords[index - 1].weight ? 'arrow-down' : 'arrow-up'}
+                        size={12}
+                        color={record.weight < weightRecords[index - 1].weight ? '#10B981' : '#EF4444'}
+                      />
+                      <ThemedText
+                        variant="caption"
+                        color={record.weight < weightRecords[index - 1].weight ? '#10B981' : '#EF4444'}
+                      >
+                        {Math.abs(record.weight - weightRecords[index - 1].weight).toFixed(1)}
+                      </ThemedText>
+                    </View>
+                  )}
+
+                  <TouchableOpacity onPress={() => deleteRecord(record.id)}>
+                    <FontAwesome6 name="trash" size={16} color={theme.textMuted} />
+                  </TouchableOpacity>
+                </View>
+              ))}
+            </View>
+          )}
+        </ThemedView>
+
+        {/* 统计信息 */}
+        {weightRecords.length >= 2 && (
+          <ThemedView level="root" style={styles.statsSection}>
+            <ThemedText variant="h4" color={theme.textPrimary} style={styles.sectionTitle}>
+              统计信息
+            </ThemedText>
+
+            <View style={styles.statRow}>
+              <View style={styles.statItem}>
+                <ThemedText variant="small" color={theme.textMuted}>
+                  初始体重
+                </ThemedText>
+                <ThemedText variant="h4" color={theme.textPrimary}>
+                  {weightRecords[weightRecords.length - 1].weight} kg
+                </ThemedText>
+              </View>
+
+              <View style={[styles.statItem, styles.statBorder]}>
+                <ThemedText variant="small" color={theme.textMuted}>
+                  当前体重
+                </ThemedText>
+                <ThemedText variant="h4" color={theme.primary}>
+                  {weightRecords[0].weight} kg
+                </ThemedText>
+              </View>
+
+              <View style={styles.statItem}>
+                <ThemedText variant="small" color={theme.textMuted}>
+                  累计变化
+                </ThemedText>
+                <ThemedText
+                  variant="h4"
+                  color={
+                    weightRecords[0].weight < weightRecords[weightRecords.length - 1].weight
+                      ? '#10B981'
+                      : '#EF4444'
+                  }
+                >
+                  {weightRecords[0].weight < weightRecords[weightRecords.length - 1].weight ? '-' : '+'}
+                  {Math.abs(
+                    weightRecords[0].weight - weightRecords[weightRecords.length - 1].weight
+                  ).toFixed(1)}{' '}
+                  kg
+                </ThemedText>
+              </View>
+            </View>
+          </ThemedView>
+        )}
+      </ScrollView>
+
+      {/* 添加记录 Modal */}
+      <Modal visible={modalVisible} transparent animationType="fade">
+        <View style={styles.modalContainer}>
+          <ThemedView level="default" style={styles.modalContent}>
+            <View style={styles.modalHeader}>
+              <ThemedText variant="h4" color={theme.textPrimary}>
+                添加体重记录
+              </ThemedText>
+              <TouchableOpacity onPress={resetModal}>
+                <FontAwesome6 name="xmark" size={24} color={theme.textSecondary} />
+              </TouchableOpacity>
+            </View>
+
+            <View style={styles.modalBody}>
+              <View style={styles.inputGroup}>
+                <ThemedText variant="small" color={theme.textSecondary} style={styles.label}>
+                  体重 (kg)
+                </ThemedText>
+                <TextInput
+                  style={styles.input}
+                  placeholder="输入体重"
+                  placeholderTextColor={theme.textMuted}
+                  value={newWeight}
+                  onChangeText={setNewWeight}
+                  keyboardType="decimal-pad"
+                />
+              </View>
+
+              <View style={styles.inputGroup}>
+                <ThemedText variant="small" color={theme.textSecondary} style={styles.label}>
+                  备注 (可选)
+                </ThemedText>
+                <TextInput
+                  style={[styles.input, styles.textArea]}
+                  placeholder="添加备注"
+                  placeholderTextColor={theme.textMuted}
+                  value={newNote}
+                  onChangeText={setNewNote}
+                  multiline
+                  numberOfLines={3}
+                />
+              </View>
+            </View>
+
+            <View style={styles.modalFooter}>
+              <TouchableOpacity
+                style={[styles.modalButton, styles.cancelButton]}
+                onPress={resetModal}
+              >
+                <ThemedText variant="smallMedium" color={theme.textSecondary}>
+                  取消
+                </ThemedText>
+              </TouchableOpacity>
+
+              <TouchableOpacity
+                style={[styles.modalButton, styles.confirmButton]}
+                onPress={addWeightRecord}
+              >
+                <ThemedText variant="smallMedium" color={theme.buttonPrimaryText}>
+                  {saving ? '保存中...' : '保存'}
+                </ThemedText>
+              </TouchableOpacity>
+            </View>
+          </ThemedView>
+        </View>
+      </Modal>
+    </Screen>
+  );
+}

client/screens/stats/styles.ts

@@ -0,0 +1,161 @@
+import { StyleSheet } from 'react-native';
+import { Spacing, BorderRadius, Theme } from '@/constants/theme';
+
+export const createStyles = (theme: Theme) => {
+  return StyleSheet.create({
+    scrollContent: {
+      flexGrow: 1,
+      paddingHorizontal: Spacing.lg,
+      paddingTop: Spacing.xl,
+      paddingBottom: Spacing["5xl"],
+    },
+    header: {
+      flexDirection: 'row',
+      justifyContent: 'space-between',
+      alignItems: 'center',
+      marginBottom: Spacing.xl,
+    },
+    addButton: {
+      width: 40,
+      height: 40,
+      borderRadius: BorderRadius.lg,
+      backgroundColor: theme.primary,
+      justifyContent: 'center',
+      alignItems: 'center',
+      shadowColor: theme.primary,
+      shadowOffset: { width: 0, height: 2 },
+      shadowOpacity: 0.2,
+      shadowRadius: 8,
+      elevation: 3,
+    },
+    chartSection: {
+      padding: Spacing.xl,
+      borderRadius: BorderRadius.xl,
+      marginBottom: Spacing.lg,
+    },
+    sectionHeader: {
+      flexDirection: 'row',
+      justifyContent: 'space-between',
+      alignItems: 'center',
+      marginBottom: Spacing.lg,
+    },
+    sectionTitle: {
+      marginBottom: Spacing.lg,
+    },
+    emptyText: {
+      textAlign: 'center',
+      paddingVertical: Spacing["2xl"],
+    },
+    recordsList: {
+      gap: Spacing.md,
+    },
+    recordItem: {
+      flexDirection: 'row',
+      justifyContent: 'space-between',
+      alignItems: 'center',
+      padding: Spacing.lg,
+      backgroundColor: theme.backgroundTertiary,
+      borderRadius: BorderRadius.lg,
+    },
+    recordInfo: {
+      flex: 1,
+    },
+    recordWeight: {
+      flexDirection: 'row',
+      alignItems: 'baseline',
+      marginBottom: Spacing.xs,
+    },
+    changeBadge: {
+      flexDirection: 'row',
+      alignItems: 'center',
+      paddingHorizontal: Spacing.sm,
+      paddingVertical: Spacing.xs,
+      backgroundColor: theme.backgroundDefault,
+      borderRadius: BorderRadius.sm,
+      marginRight: Spacing.md,
+    },
+    statsSection: {
+      padding: Spacing.xl,
+      borderRadius: BorderRadius.xl,
+      marginBottom: Spacing.lg,
+    },
+    statRow: {
+      flexDirection: 'row',
+      justifyContent: 'space-between',
+    },
+    statItem: {
+      flex: 1,
+      alignItems: 'center',
+    },
+    statBorder: {
+      borderLeftWidth: 1,
+      borderRightWidth: 1,
+      borderColor: theme.border,
+    },
+    modalContainer: {
+      flex: 1,
+      backgroundColor: 'rgba(0, 0, 0, 0.5)',
+      justifyContent: 'center',
+      alignItems: 'center',
+      padding: Spacing.lg,
+    },
+    modalContent: {
+      width: '100%',
+      maxWidth: 400,
+      borderRadius: BorderRadius["2xl"],
+    },
+    modalHeader: {
+      flexDirection: 'row',
+      justifyContent: 'space-between',
+      alignItems: 'center',
+      padding: Spacing.xl,
+      borderBottomWidth: 1,
+      borderBottomColor: theme.border,
+    },
+    modalBody: {
+      padding: Spacing.xl,
+    },
+    inputGroup: {
+      marginBottom: Spacing.lg,
+    },
+    label: {
+      marginBottom: Spacing.sm,
+    },
+    input: {
+      backgroundColor: theme.backgroundTertiary,
+      borderRadius: BorderRadius.lg,
+      paddingHorizontal: Spacing.lg,
+      paddingVertical: Spacing.md,
+      color: theme.textPrimary,
+      fontSize: 16,
+    },
+    textArea: {
+      height: 80,
+      textAlignVertical: 'top',
+    },
+    modalFooter: {
+      flexDirection: 'row',
+      gap: Spacing.md,
+      padding: Spacing.xl,
+      borderTopWidth: 1,
+      borderTopColor: theme.border,
+    },
+    modalButton: {
+      flex: 1,
+      paddingVertical: Spacing.lg,
+      borderRadius: BorderRadius.lg,
+      alignItems: 'center',
+    },
+    cancelButton: {
+      backgroundColor: theme.backgroundTertiary,
+    },
+    confirmButton: {
+      backgroundColor: theme.primary,
+      shadowColor: theme.primary,
+      shadowOffset: { width: 0, height: 2 },
+      shadowOpacity: 0.2,
+      shadowRadius: 8,
+      elevation: 3,
+    },
+  });
+};