Fix GitHub Actions to use bundler with updated dependencies

- Switch from manual gem installation to bundler-cache approach
- Use 'bundle exec jekyll build' to respect Gemfile.lock versions
- Leverage ruby/setup-ruby bundler caching for faster builds
- Resolves Jekyll 4.4.1 and dependency version mismatches

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

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

Author: ulfarsson

.github/workflows/jekyll.yml

@@ -32,24 +32,15 @@ jobs:
         uses: ruby/setup-ruby@v1
         with:
           ruby-version: '3.3.9'
-          bundler: none  # Don't install bundler at all
-
-      - name: Install dependencies
-        run: |
-          gem install jekyll -v 4.4.0
-          gem install minima -v 2.5.2
-          gem install jekyll-feed -v 0.17.0
-          gem install jekyll-sitemap -v 1.4.0
-          gem install jekyll-seo-tag -v 2.8.0
-          gem install webrick -v 1.9.1
+          bundler-cache: true
 
       - name: Setup Pages
         id: pages
         uses: actions/configure-pages@v5
 
       - name: Build with Jekyll
         # Outputs to the './_site' directory by default
-        run: jekyll build --baseurl "${{ steps.pages.outputs.base_path }}"
+        run: bundle exec jekyll build --baseurl "${{ steps.pages.outputs.base_path }}"
         env:
           JEKYLL_ENV: production