fix(navbar): show theme toggle on mobile screens

[OmkarArdekar12]

Description

Fixes #889

This PR fixes the issue where the theme toggle button was not visible on small/mobile screen sizes.

Previously, the theme toggle button was placed inside a desktop-only container, causing it to disappear on smaller devices. This update ensures that the theme toggle remains accessible across mobile, tablet, and desktop screen sizes while preserving the existing responsive navbar behavior.

Changes Made

• Fixed responsive visibility issue for the theme toggle button
• Added proper mobile accessibility for theme switching
• Preserved existing desktop navbar layout
• Improved responsive navigation experience across different screen sizes

Pillar

• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

Desktop View

Tablet / Large Mobile View

Mobile View

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors.
• My commits follow the Conventional Commits format.
• I have made sure that only relevant files are included in this PR.
• I have made sure that I have only one commit to merge in this PR.
• The UI remains responsive across different screen sizes.
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

@JhaSourav07 Kindly review this PR. Thank you!

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[github-actions]

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