fix: replace sun and moon icons to correct uneven spacing in theme toggle

[MAY55A]

Pull Request description

This pull request fixes uneven spacing due to using text icons for the theme toggle instead of an svg or icon element.
Icons from lucide-react library have been used to correct this.

fixes #136

Pull Request checklists

This PR is a:

• bug-fix
• new feature
• maintenance

About this PR:

• it includes tests.
• the tests are executed on CI.
• pre-commit hooks were executed locally.
• this PR requires a project documentation update.

Author's checklist:

• I have reviewed the changes and it contains no misspelling.
• The code is well commented, especially in the parts that contain more
  complexity.
• New and old tests passed locally.

Additional information

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• After:

Reviewer's checklist

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## Reviewer's Checklist

- [ ] I managed to reproduce the problem locally from the `main` branch
- [ ] I managed to test the new changes locally
- [ ] I confirm that the issues mentioned were fixed/resolved.

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[yuvimittal]

@MAY55A , please rebase your branch

[MAY55A]

Hi @yuvimittal , I updated the branch, you can check it out.

[sanvishukla]

@yuvimittal, please merge this, it looks good to me