fix(ui): always show background on mobile navbar to prevent contrast issues

components/Header.tsx

@@ -101,7 +101,7 @@ export default function Header() {
   const headerClass = cn(
     'fixed top-0 left-0 right-0 z-50 transition-all duration-500 safe-area-p transform-gpu animate-in fade-in slide-in-from-top-12 fill-mode-both',
     {
-      'bg-transparent py-4 md:py-8': isHomePage && !isScrolled && !isMobileMenuOpen,
+      'bg-primary/95 backdrop-blur-md md:bg-transparent py-3 md:py-8 shadow-2xl md:shadow-none': isHomePage && !isScrolled && !isMobileMenuOpen,
       'bg-primary py-3 md:py-4 shadow-2xl': !isHomePage || isScrolled || isMobileMenuOpen,
     },
   );