Update Jekyll and plugins to latest versions

- Update Jekyll from 4.3.0 to 4.4.1
- Update jekyll-feed to 0.17
- Update jekyll-sitemap to 1.4
- Update jekyll-seo-tag to 2.8

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: theodorosploumis

Gemfile

@@ -1,15 +1,15 @@
 source 'https://rubygems.org'
 
 # Jekyll and GitHub Pages
-gem 'jekyll', '~> 4.3.0'
+gem 'jekyll', '~> 4.4.1'
 gem 'liquid'
 gem "webrick", "~> 1.8"
 
 # GitHub Pages compatible plugins
 group :jekyll_plugins do
-  gem 'jekyll-feed'
-  gem 'jekyll-sitemap'
-  gem 'jekyll-seo-tag'
+  gem 'jekyll-feed', '~> 0.17'
+  gem 'jekyll-sitemap', '~> 1.4'
+  gem 'jekyll-seo-tag', '~> 2.8'
 end
 
 # Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem