refactor: Update layout and styling in various components for improved responsiveness and visual consistency on mobile; adjust zIndex and position properties, and enhance navigation handling in ProductDetailPage

src/PrerenderProduct.js

@@ -165,16 +165,15 @@ class PrerenderProduct extends React.Component {
             sx: {
               mb: 2,
               position: ["-webkit-sticky", "sticky"],
+              // No CategoryList in prerender — two-row toolbar only; safe-area for notched phones.
               top: {
-                xs: "80px",
+                xs: "calc(env(safe-area-inset-top, 0px) + 128px)",
                 sm: "80px",
-                md: "80px",
-                lg: "80px",
               },
               left: 0,
               width: "100%",
               display: "flex",
-              zIndex: 999, // Just below the AppBar
+              zIndex: (theme) => theme.zIndex.appBar - 1,
               py: 0,
               px: 2,
             }