Implement theme system

[compscidr]

Summary

Introduces a WordPress-style theme system. Templates and theme-specific CSS now live in themes/{name}/ directories, and the active theme is configurable via the theme admin setting.

Directory structure

themes/
  default/
    templates/        # All HTML templates
      header.html
      footer.html
      admin_nav.html  # NEW: shared admin navigation (was duplicated 9x)
      post.html
      home.html
      ...
    static/           # Theme CSS/assets (served at /theme/)
      css/
        goblog.css

How to create a new theme

1. Copy themes/default/ to themes/my-theme/
2. Customize the templates and CSS
3. Set the theme setting to my-theme in admin settings
4. Restart the server

Changes

• Move all templates from templates/ → themes/default/templates/
• Move www/css/goblog.css → themes/default/static/css/goblog.css
• Load templates from themes/{active_theme}/templates/ based on the theme setting
• Serve theme static files at /theme/ URL path
• Extract duplicated admin nav into shared admin_nav.html partial — was copy-pasted across 9 admin templates with hardcoded active states. Now uses JS to highlight the active link based on the current URL.
• Add theme setting to seed defaults (value: "default")

What stays in www/

General static assets that aren't theme-specific: favicon, images, uploads, admin-script.js, site.webmanifest, etc.

Closes #481

Test plan

• All existing tests pass
• Start server — templates load from themes/default/
• CSS loads from /theme/css/goblog.css
• Admin nav highlights the correct active page
• Copy themes/default/ to themes/custom/, change something, set theme=custom — custom theme loads

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR introduces a theme-based template/static loading mechanism (with a new default theme) and adds a set of new HTML templates for the blog, admin UI, and install wizard flows.

Changes:

• Add a theme setting and load templates/static assets from themes/<theme>/... (defaulting to default).
• Introduce the themes/default theme (templates + CSS) including install wizard pages and multiple blog/admin pages.
• Refactor admin navigation into a shared admin_nav.html include.

Reviewed changes

Copilot reviewed 15 out of 41 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tools/migrate.go	Seeds a new default theme setting (default).
goblog.go	Loads templates from the active theme directory and serves theme static assets under /theme/.
blog/blog_test.go	Updates test template glob path to the new default theme templates.
admin/admin_test.go	Updates test template glob path to the new default theme templates.
themes/default/static/css/goblog.css	Adds theme-specific CSS (now served via /theme/css/goblog.css).
themes/default/templates/header.html	Updates stylesheet path to /theme/css/goblog.css.
themes/default/templates/footer.html	Adds new footer layout and “Most Recent Post” section.
themes/default/templates/admin_nav.html	New shared admin navigation partial + active link script.
themes/default/templates/admin.html	Switches to using admin_nav.html.
themes/default/templates/admin_all_posts.html	Switches to using admin_nav.html.
themes/default/templates/admin_dashboard.html	Switches to using admin_nav.html.
themes/default/templates/admin_new_post.html	Switches to using admin_nav.html.
themes/default/templates/admin_pages.html	Switches to using admin_nav.html.
themes/default/templates/admin_edit_page.html	Switches to using admin_nav.html.
themes/default/templates/admin_post_types.html	Switches to using admin_nav.html.
themes/default/templates/admin_edit_post_type.html	Switches to using admin_nav.html.
themes/default/templates/admin_settings.html	Switches to using admin_nav.html.
themes/default/templates/wizard_db.html	New DB setup wizard page with AJAX “test DB”.
themes/default/templates/wizard_settings.html	New settings wizard page that posts settings via JS.
themes/default/templates/wizard_auth.html	New GitHub OAuth wizard page for client id/secret.
themes/default/templates/wizard_success.html	New wizard completion page with timed redirect.
themes/default/templates/home.html	New home/landing page template.
themes/default/templates/login.html	New login page template with GitHub OAuth flow script.
themes/default/templates/post.html	New post view template with markdown rendering + comments UI.
themes/default/templates/post-admin.html	New post admin editor template with preview + revisions.
themes/default/templates/posts.html	New posts listing template.
themes/default/templates/search.html	New search page template and results listing.
themes/default/templates/tags.html	New tags index template.
themes/default/templates/tag.html	New single-tag listing template.
themes/default/templates/archives.html	New archives index template.
themes/default/templates/page_archives.html	New archives page template variant using year/month groupings.
themes/default/templates/page_content.html	New generic “page markdown content” renderer template.
themes/default/templates/page_research.html	New research page template variant.
themes/default/templates/page_tags.html	New tags page template variant.
themes/default/templates/page_writing.html	New writing page template listing posts.
themes/default/templates/post_type_listing.html	New post-type listing template.
themes/default/templates/research.html	New research/publications template.
themes/default/templates/projects.html	New projects page template (video hero + placeholder text).
themes/default/templates/presentations.html	New presentations/speaking template (placeholder text).
themes/default/templates/about.html	New about page template content.
themes/default/templates/error.html	New error page template.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.