Refactor components and enhance background task management

- Updated font sizes and weights in BasalMetabolismCard, MoodCard, HealthDataCard, and NutritionRadarCard for improved readability.
- Removed loading state from MoodCard to simplify the component.
- Adjusted styles in WeightHistoryCard for better layout and spacing.
- Integrated expo-background-fetch for improved background task handling.
- Updated Info.plist to include background fetch capability.
- Enhanced background task registration and execution logic in backgroundTaskManager.
- Added debug function to manually trigger background task execution for testing purposes.

components/weight/WeightHistoryCard.tsx

@@ -195,19 +195,6 @@ export function WeightHistoryCard() {
     };
   });
 
-  // 如果正在加载，显示加载状态
-  if (isLoading) {
-    return (
-      <TouchableOpacity style={styles.card} onPress={navigateToWeightRecords} activeOpacity={0.8}>
-        <View style={styles.cardHeader}>
-          <Text style={styles.cardTitle}>体重记录</Text>
-        </View>
-        <View style={styles.emptyContent}>
-          <Text style={styles.emptyDescription}>加载中...</Text>
-        </View>
-      </TouchableOpacity>
-    );
-  }
 
   // 如果没有体重数据，显示引导卡片
   if (!hasWeight) {
@@ -574,6 +561,7 @@ const styles = StyleSheet.create({
     shadowOpacity: 0.1,
     shadowRadius: 8,
     elevation: 3,
+    marginTop: 16
   },
   cardHeader: {
     flexDirection: 'row',
@@ -649,6 +637,7 @@ const styles = StyleSheet.create({
   summaryInfo: {
     position: 'absolute',
     width: '100%',
+    marginTop: 10,
   },
   chartContainer: {
     position: 'absolute',