Follow-up to #1645: Restore valid resources and catch additional dead links

[mikeyil]

Description

This is a follow-up to PR #1645 to address the dead links reported in #1647.

I saw that some of the resources deleted in #1645 had simply moved to new URLs, while other dead links had been missed entirely. This PR restores those valid resources and does additional cleanup.

Changes Made

• Restored 4 resources that were deleted in Fix: replace dead color contrast checker link with active tool #1645 by tracking down their new URLs:
  • Alicia Jarvis' Inclusive Design Blog -> alicia.design
  • Apps For All -> Smashing Magazine's new book store URL
  • Inclusive Design Patterns -> Smashing Magazine's new book store URL
  • Inclusion: Diversity, The New Workplace -> jenniferbrownspeaks.com/books/
• Removed 12 completely dead links, including 8 from the original issue, plus 4 additional broken links that were discovered during our audit (tota11y, Accessible Podcast, Simply Open, and DMOZ list).
• Added David Mello's WCAG Color Contrast Checker (preserving the addition from Fix: replace dead color contrast checker link with active tool #1645 to replace the defunct Josef Eines tool).

Why the links were removed

For historical context, the 12 removed links were confirmed completely down:

• tota11y: Abandoned project (last update 3+ years ago)
• Color Contrast Checker: Host alarmsystem.no is down
• Future Date: Heroku eliminated free tiers, taking down the site
• Thinking about Digital Accessibility: The Everand link is 404
• Considerations when writing alt text: Removed from the Shopify UX blog
• Introduction to Web Accessibility: Dr. Michele Williams rebranded her site, resulting in a 404
• Giving a damn about accessibility: The uxdesign.cc subdomain is dead
• PDF accessibility introduction: pragmaticaccess.com is unreachable
• Accessibility for Teams: The accessibility.digital.gov subdomain fails DNS resolution
• Accessible Podcast: The timothybuck.me archive is 404
• Simply Open: simplyopen.io domain is unreachable
• List of online accessibility tools: DMOZ is defunct

Fixes #1647