feat: Implement Food Camera Screen and Floating Food Overlay

- Added FoodCameraScreen for capturing food images with camera functionality.
- Integrated image picker for selecting images from the gallery.
- Created FloatingFoodOverlay for quick access to food library and scanning options.
- Updated NutritionRadarCard to utilize FloatingFoodOverlay for adding food.
- Enhanced ExploreScreen layout and styles for better user experience.
- Removed unused SafeAreaView from ExploreScreen.
- Updated profile edit screen to remove unnecessary state variables.
- Updated avatar image source in profile edit screen.
- Added ExpoCamera dependency for camera functionalities.

components/ui/HeaderBar.tsx

@@ -9,6 +9,7 @@ import { useColorScheme } from '@/hooks/useColorScheme';
 export type HeaderBarProps = {
   title: string | React.ReactNode;
   onBack?: () => void;
+  backColor?: string;
   right?: React.ReactNode;
   tone?: 'light' | 'dark';
   showBottomBorder?: boolean;
@@ -20,6 +21,7 @@ export type HeaderBarProps = {
 export function HeaderBar({
   title,
   onBack,
+  backColor,
   right,
   tone,
   showBottomBorder = false,
@@ -34,7 +36,7 @@ export function HeaderBar({
   // 根据变体确定背景色和样式
   const getBackgroundColor = () => {
     if (transparent) return 'transparent';
-    
+
     switch (variant) {
       case 'elevated':
         return theme.background;
@@ -47,11 +49,11 @@ export function HeaderBar({
 
   const getBorderStyle = () => {
     if (!showBottomBorder) return {};
-    
+
     return {
       borderBottomWidth: 1,
-      borderBottomColor: variant === 'elevated' 
-        ? theme.border 
+      borderBottomColor: variant === 'elevated'
+        ? theme.border
         : `${theme.border}40`, // 40% 透明度
     };
   };
@@ -75,16 +77,16 @@ export function HeaderBar({
       ]}
     >
       {onBack ? (
-        <TouchableOpacity 
-          accessibilityRole="button" 
-          onPress={onBack} 
+        <TouchableOpacity
+          accessibilityRole="button"
+          onPress={onBack}
           style={styles.backButton}
           activeOpacity={0.7}
         >
-          <Ionicons 
-            name="chevron-back" 
-            size={24} 
-            color={theme.text} 
+          <Ionicons
+            name="chevron-back"
+            size={24}
+            color={backColor || theme.text}
           />
         </TouchableOpacity>
       ) : (
@@ -94,8 +96,8 @@ export function HeaderBar({
       <View style={styles.titleContainer}>
         {typeof title === 'string' ? (
           <Text style={[
-            styles.title, 
-            { 
+            styles.title,
+            {
               color: theme.text,
               fontWeight: variant === 'elevated' ? '700' : '800',
             }