fix: replace invalid Tailwind utility classes

[YLaxmikanth]

📌 Description

Fixed multiple invalid and undefined Tailwind CSS utility classes across the frontend to ensure proper styling behavior and avoid silent failures.

🔗 Related Issue

Closes #834

🛠 Changes Made

• Replaced pt-15 with pt-16
• Replaced py-15 with py-16
• Replaced z-100 with z-50
• Replaced undefined bg-soft with bg-[var(--border)]
• Verified no invalid Tailwind classes remain in frontend/src

✅ Checklist

• Code runs locally
• Followed project structure
• No console errors
• Properly tested changes
• Linked the issue

🚀 Notes for Reviewers

Verified the frontend builds successfully using npm run build and ensured all invalid Tailwind utility classes were removed.