feat: 集成健康数据功能

- 在项目中引入 react-native-health 库以获取健康数据
- 在 Explore 页面中添加步数和能量消耗的显示
- 实现页面聚焦时自动拉取今日健康数据
- 更新 iOS 权限设置以支持健康数据访问
- 添加健康数据相关的工具函数以简化数据获取

utils/health.ts

@@ -0,0 +1,53 @@
+import AppleHealthKit, { HealthKitPermissions } from 'react-native-health';
+
+const PERMISSIONS: HealthKitPermissions = {
+  permissions: {
+    read: [
+      AppleHealthKit.Constants.Permissions.StepCount,
+      AppleHealthKit.Constants.Permissions.ActiveEnergyBurned,
+    ],
+    write: [],
+  },
+};
+
+export type TodayHealthData = {
+  steps: number;
+  activeEnergyBurned: number; // kilocalories
+};
+
+export async function ensureHealthPermissions(): Promise<boolean> {
+  return new Promise((resolve) => {
+    AppleHealthKit.initHealthKit(PERMISSIONS, (error) => {
+      if (error) {
+        console.warn('HealthKit init failed', error);
+        resolve(false);
+        return;
+      }
+      console.log('HealthKit init success');
+      resolve(true);
+    });
+  });
+}
+
+export async function fetchTodayHealthData(): Promise<TodayHealthData> {
+  const start = new Date();
+  start.setHours(0, 0, 0, 0);
+  const options = { startDate: start.toISOString() } as any;
+
+  const steps = await new Promise<number>((resolve) => {
+    AppleHealthKit.getStepCount(options, (err, res) => {
+      if (err || !res) return resolve(0);
+      resolve(res.value || 0);
+    });
+  });
+
+  const calories = await new Promise<number>((resolve) => {
+    AppleHealthKit.getActiveEnergyBurned(options, (err, res) => {
+      if (err || !res) return resolve(0);
+      // library returns value as number in kilocalories
+      resolve(res[0].value || 0);
+    });
+  });
+
+  return { steps, activeEnergyBurned: calories };
+}