Implement responsive improvements for AppShell navigation

[Dippp10-ally]

---

Description

This PR adds responsive styles to the AppShell navigation to improve usability and layout on smaller screen sizes. The navigation now adapts properly across different breakpoints, ensuring better accessibility and visual consistency on mobile and tablet devices.

Related Issues

Closes #427

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature / enhancement (non-breaking change that improves responsiveness)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Changes Made

• Added responsive styling rules for AppShell navigation
• Improved layout behavior on smaller screens (mobile/tablet)
• Ensured navigation elements remain accessible and usable across breakpoints
• Adjusted spacing/alignment for better visual hierarchy on compact screens

How Has This Been Tested?

• Tested on multiple screen sizes using browser dev tools (mobile, tablet, desktop)
• Verified navigation visibility and usability at different breakpoints
• Checked for layout overflow and overlapping elements
• Confirmed no UI regressions on existing desktop layout

Checklist

• My code follows the code style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

---

[Dippp10-ally]

@utksh1 ji , i have implemented changes you requested in pull request number 431 and have closed pull request number 428......do assign labels called as gssoc:approved , level:intermediate , type:feature , quality:exceptional to above pull request number 431....do merge pull request number 431 also......

[utksh1]

Looks good: applies responsive adjustments to the actual AppShell/navigation and layout selectors, unlike the earlier generic navbar-only PR. Checks are green.

[Dippp10-ally]

@utksh1 ji ,do assign label called as quality:exceptional to above pull request number 431 also........do merge above pull request number 431 also.....