Fix: Improve icon contrast and text hierarchy Contributing and About Pages

[michellecaii]

Because

The About page's belief section currently uses low-contrast icons and tight typography, especially in dark mode. This affects both accessibility and visual engagement.

This PR

• Updates icon styling to use high-contrast background and foreground colors for better accessibility in both light and dark modes

• Enlarges icons and wraps them in rounded backgrounds to make them more visually prominent

• Improves heading size and spacing for clearer text hierarchy

Issue

Additional Information

Pull Request Requirements

• [x] I have thoroughly read and understand The Odin Project Contributing Guide
• [x] The title of this PR follows the keyword: brief description of change format, using one of the following keywords:
  • Feature - adds new or amends existing user-facing behavior
  • Chore - changes that have no user-facing value, refactors, dependency bumps, etc
  • Fix - bug fixes
• [x] The Because section summarizes the reason for this PR
• [x] The This PR section has a bullet point list describing the changes in this PR
• [x] I have verified all tests and linters pass after making these changes.
• [x] If this PR addresses an open issue, it is linked in the Issue section
• [x] If applicable, this PR includes new or updated automated tests

[KevinMulhern]

Hey @michellecaii, just checking in, do you want to finish this PR?