fix: improve navbar styling for light theme

[C4aZy]

📝 Description

Improved the navbar appearance in light theme mode.

🔗 Linked Issue

Closes #439

---

📋 Contribution Checklist

• My code strictly adheres to the project guidelines (Standard library only, procedural code, clean spacing).
• I have verified that my files are placed in the correct directory.
• I have tested my changes thoroughly on my local machine.
• I have included interactive emojis and clean console/UI outputs.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

[vercel]

@C4aZy is attempting to deploy a commit to the Anuj's projects Team on Vercel.

A member of the Team first needs to authorize it.

[C4aZy]

@steam-bell-92 Please review.

[github-actions]

🎉 Thank you for your contribution!

Your Pull Request has been merged successfully.

We appreciate the time and effort you put into improving this project. Contributions like yours help the repository grow and stay useful for everyone.

If you'd like to contribute again, please check the open issues and make sure you are assigned before opening another Pull Request.

Thanks again for your support! 🙌