Refactor: Remove background task management and related hooks

- Deleted `useBackgroundTasks.ts` hook and its associated logic for managing background tasks.
- Removed `backgroundTaskManager.ts` service and all related task definitions and registrations.
- Cleaned up `Podfile.lock` and `package.json` to remove unused dependencies related to background tasks.
- Updated iOS project files to eliminate references to removed background task components.
- Added new background fetch identifier in `Info.plist` for future use.

components/FloatingFoodOverlay.tsx

@@ -33,7 +33,7 @@ export function FloatingFoodOverlay({ visible, onClose, mealType = 'dinner' }: F
   const menuItems = [
     {
       id: 'scan',
-      title: 'AI拍照识别',
+      title: 'AI识别',
       icon: '📷',
       backgroundColor: '#4FC3F7',
       onPress: handlePhotoRecognition,
@@ -56,7 +56,7 @@ export function FloatingFoodOverlay({ visible, onClose, mealType = 'dinner' }: F
       onRequestClose={onClose}
 
     >
-      <View style={styles.overlay}>
+      <BlurView intensity={20} tint="dark" style={styles.overlay}>
         <TouchableOpacity
           style={styles.backdrop}
           activeOpacity={1}
@@ -96,7 +96,7 @@ export function FloatingFoodOverlay({ visible, onClose, mealType = 'dinner' }: F
             </View>
           </TouchableOpacity>
         </View>
-      </View>
+      </BlurView>
     </Modal>
   );
 }
@@ -104,8 +104,7 @@ export function FloatingFoodOverlay({ visible, onClose, mealType = 'dinner' }: F
 const styles = StyleSheet.create({
   overlay: {
     flex: 1,
-    backgroundColor: 'rgba(0, 0, 0, 0.4)',
-    justifyContent: 'center',
+    justifyContent: 'flex-end',
     alignItems: 'center',
   },
   backdrop: {
@@ -117,6 +116,7 @@ const styles = StyleSheet.create({
   },
   container: {
     alignItems: 'center',
+    marginBottom: 40,
   },
   blurContainer: {
     borderRadius: 20,
@@ -132,9 +132,9 @@ const styles = StyleSheet.create({
     alignItems: 'center',
   },
   title: {
-    fontSize: 16,
+    fontSize: 12,
     fontWeight: '600',
-    color: '#333',
+    color: '#636161ff',
   },
   menuGrid: {
     flexDirection: 'row',
@@ -146,9 +146,9 @@ const styles = StyleSheet.create({
     flex: 1,
   },
   iconContainer: {
-    width: 48,
-    height: 48,
-    borderRadius: 24,
+    width: 40,
+    height: 40,
+    borderRadius: 20,
     alignItems: 'center',
     justifyContent: 'center',
     marginBottom: 8,
@@ -162,7 +162,7 @@ const styles = StyleSheet.create({
     elevation: 4,
   },
   iconText: {
-    fontSize: 22,
+    fontSize: 16,
   },
   menuText: {
     fontSize: 13,