Add responsive styles for navbar and mobile menu

[Dippp10-ally]

Navbar UI/UX Improvements

Description of Changes

This PR introduces improvements to the navigation bar to enhance responsiveness, usability, and overall user experience across different devices and screen sizes.

Changes Included

• Improved navbar responsiveness for mobile, tablet, and desktop viewports.
• Added better spacing and alignment for navigation items.
• Enhanced mobile navigation experience with optimized menu behavior.
• Improved accessibility through better focus states and keyboard navigation support.
• Added smoother transitions and hover effects for navigation elements.
• Fixed layout and overflow issues on smaller screens.
• Ensured consistent appearance across light and dark themes.

Related Issue Number

Fixes #226

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor or other maintenance

How Was This Tested?

• Tested navbar behavior on mobile, tablet, and desktop screen sizes.
• Verified responsive menu functionality and navigation interactions.
• Checked keyboard accessibility and focus states.
• Confirmed compatibility with light and dark themes.
• Ensured there were no layout shifts or overflow issues during navigation.

Checklist

• The code builds without errors (npm run build).
• Existing tests pass (npm test).
• New tests have been added if needed.
• Documentation has been updated to reflect these changes if needed.

[Dippp10-ally]

@ThePlator ji , do assign labels called as gssoc:approved , level:intermediate , type:feature , quality:exceptional to above pull request number 227 also....do merge above pull request number 227 also........

[Dippp10-ally]

@ThePlator ji , below is screenshot prior to making changes.......

[Dippp10-ally]

@ThePlator ji , below are screenshots after making changes.....

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