Simplify page layout by removing right-side widgets and restore Pages workflow

[Copilot]

Page-based views were still carrying the right-side FEATURED TAGS / ABOUT ME sidebar chrome, which made the simplified navigation pages feel cluttered. This PR removes that sidebar from the shared page layout and restores the GitHub Pages build workflow file to the master branch version.

• Page layout cleanup

  • removed the shared right-side sidebar from _layouts/page.html
  • page-based views now render as a single centered content column
  • this drops the page-level sidebar widgets:
    • FEATURED TAGS
    • ABOUT ME
    • FRIENDS

• Affected views

  • homepage
  • about page
  • folder/listing pages using the shared page layout

• Workflow restoration

  • restored .github/workflows/site-build.yml to match master
  • brings back Pages-specific permissions, configure-pages, artifact upload, and deploy job

Example of the layout change:

<div class="container">
  <div class="row">
    <div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1 postlist-container">
      {{ content }}
    </div>
  </div>
</div>