feature: enhance MobileMegaMenu with structured layout, performance, …

[JExcellence]

…and consistent interactivity

• Refactored component to follow layout and interactivity principles using Flex/Grid and ElementType
• Improved performance and accessibility by avoiding unnecessary renders and normalizing keys
• Replaced inline styles and classes with SCSS module and classNames utility
• Ensured external links are safe via rel="noopener noreferrer"
• Used ReactNode for flexible label/description rendering
• Added support for aria-expanded states on toggles
• Applied project conventions: PascalCase naming, displayName, and use client directive

javascript { isMobileMenuOpen && ( <Column fillWidth position="absolute" top="0" left="0" center> <MobileMegaMenu menuGroups={menuGroups} onClose={() => setIsMobileMenuOpen(false)}/> </Column> )}