Update Twitter branding and improve footer social media link presentation

## Summary

Twitter branding is still visible in multiple user-facing sections of the website. Additionally, the footer currently displays social media links primarily as text rather than standardized icons.

## Verification

- Verified on the deployed website.
- Verified locally using `bundle exec jekyll serve`.

## Current Behavior

### Twitter Branding

Twitter branding and Twitter-specific assets are still visible in:

- Footer social links
- Community page social section
- Home page social section

### Footer Social Links

The footer displays text-based social links rather than standardized social media icons.

## Relevant Files Identified

- `_config.yml`
- `_pages/community.md`
- `_pages/home.md`
- `_includes/author-profile.html`

## Screenshots

## Proposed Solution

- Update user-facing Twitter branding to X where appropriate.
- Review social media icons and labels for consistency.
- Improve footer social link presentation and hover/focus feedback.

I would be happy to contribute a fix for this issue. Feedback on the proposed approach would be appreciated before I start working on a pull request.