fix(store): position categories view below dynamic island using reactive safe area top reader & refactor layout components

pedi-foods/Sources/PediFoods/Views/Main/StoreDetailSupport.swift

@@ -61,3 +61,31 @@ struct AsyncStoreImage: View {
             .scaledToFill()
     }
 }
+
+struct SafeAreaTopPreferenceKey: PreferenceKey {
+    static let defaultValue: CGFloat = 0
+    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
+        let next = nextValue()
+        if next > 0 {
+            value = next
+        }
+    }
+}
+
+struct SafeAreaTopReader: View {
+    @Binding var safeAreaTop: CGFloat
+
+    var body: some View {
+        GeometryReader { geometry in
+            Color.clear
+                .preference(key: SafeAreaTopPreferenceKey.self, value: geometry.safeAreaInsets.top)
+        }
+        .frame(height: 0)
+        .onPreferenceChange(SafeAreaTopPreferenceKey.self) { value in
+            if value > 0 && safeAreaTop != value {
+                safeAreaTop = value
+            }
+        }
+    }
+}
+