[REFACTOR] Move Inline Styles from journey.html to External CSS

[Jbhawal]

What's the current process?

The journey.html file contains inline <style> blocks, making the file lengthy and mixing structure with presentation. Other pages in the project already follow the practice of keeping styles in separate CSS files.

What can be improved?

• Extract the inline styles from journey.html into a dedicated CSS file (e.g., journey.css).
• Ensure journey.html only handles content and structure, while CSS files handle styling.
• Maintain consistency by following the same structure as the other pages.

How will this help?

• Keeps the HTML file cleaner and easier to read.
• Centralizes styling, making it easier to update or fix design issues in the future.
• Aligns with best practices and ensures consistency with the rest of the codebase.

[github-actions]

Thank you for raising this issue!

We'll review it as soon as possible. We truly appreciate your contributions! ✨

Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊

[Jbhawal]

I would like to work on this as a GSSOC contributor. Please assign me this with relevant labels.