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.

app/food-library.tsx

@@ -527,7 +527,7 @@ export default function FoodLibraryScreen() {
 const styles = StyleSheet.create({
   container: {
     flex: 1,
-    backgroundColor: '#F8F9FA',
+    backgroundColor: Colors.light.pageBackgroundEmphasis,
   },
   customButton: {
     paddingHorizontal: 8,