feat: redesign header with premium responsive UI

[aditi123-hub]

Summary

Redesigned the Product Store header to provide a more premium, modern, and professional user experience while maintaining responsiveness and dark/light mode compatibility.

Changes Made

• Added improved header styling with better visual hierarchy
• Enhanced sticky header appearance with refined shadow and border transitions
• Improved search bar styling and usability
• Unified action button styling with consistent hover interactions
• Enhanced responsive behavior for desktop and mobile layouts
• Improved cart drawer UI consistency
• Maintained full dark/light mode compatibility

Testing

• Tested in desktop view
• Tested in mobile view
• Verified sticky header behavior
• Verified dark mode functionality
• Verified search functionality
• Ran lint successfully
• Ran production build successfully

Build Verification

npm run lint
npm run build

Both commands completed successfully.

Screenshots

Before

After - Light Mode

After - Dark Mode

After - Mobile View

Closes #6

[vercel]

@aditi123-hub is attempting to deploy a commit to the niharika-mente's projects Team on Vercel.

A member of the Team first needs to authorize it.

[Aamod-Dev]

Substantial UI overhaul of the header — glassmorphism, scroll-aware shadow, improved cart drawer, cleaner mobile menu. All logic preserved. Screenshots confirm the visual improvement. LGTM.