fix: correct MiniNavbar width breakpoint comparisons

[AliRana30]

Description

This PR fixes MiniNavbar responsive width logic by replacing string-based viewport breakpoint comparisons with numeric comparisons.

Related Issue

Closes #387

Motivation and Context

The responsive search input width in MiniNavbar was computed using string literals for breakpoint checks.
Breakpoint logic should be numeric to avoid inconsistent behavior across screen sizes.

How Has This Been Tested?

• Verified code change is minimal and isolated to MiniNavbar responsive width condition.
• Manually reviewed breakpoint logic for 575px–959px range behavior.

Screenshots or GIF (In case of UI changes):

500px or more :

350-500px:

300-350px :

Types of changes

• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.