Remediate open Ruby dependency vulnerabilities by removing blocked sqlite3 chain and upgrading patched gems

[Copilot]

This PR addresses open security vulnerabilities in the Ruby dependency graph (prioritizing Dependabot remediation) and updates the repo to a vulnerability-free lockfile state. The key blocker was a transitive sqlite3 constraint that prevented upgrading to a patched line.

• Alert remediation summary

  • Eliminated the vulnerable sqlite3 chain by removing jekyll_ai_related_posts (it pinned sqlite3 ~> 1.4, incompatible with patched advisory requirements).
  • Upgraded remaining vulnerable gems in Gemfile.lock to patched versions:
    • concurrent-ruby 1.3.6 → 1.3.8 (patched >= 1.3.7)
    • json 2.19.4 → 2.21.1 (patched >= 2.19.9)
    • nokogiri 1.18.6 → 1.19.4 (patched >= 1.19.4)
  • Removed vulnerable transitive dependencies introduced by the removed plugin, including faraday and sqlite3.

• Dependency/config changes

  • Gemfile
    • Removed: gem 'jekyll_ai_related_posts', git: 'https://github.com/stevenjmesser/jekyll_ai_related_posts.git'
  • _config.yml
    • Removed jekyll_ai_related_posts from plugins
    • Removed ai_related_posts config block
    • Removed related sqlite cache excludes tied to that plugin
  • Gemfile.lock
    • Regenerated to reflect patched dependency graph and current platforms.

• Representative change

# Gemfile
- gem 'jekyll_ai_related_posts', git: 'https://github.com/stevenjmesser/jekyll_ai_related_posts.git'