Consolidate all moonweb sites into single Eleventy config

- Single eleventy.config.js at root with computed pathPrefix per section
- Accent colors inlined in base.njk (no per-site theme.css needed)
- Hub pages output at root via explicit permalinks
- Per-section sitemaps with tag-based collections
- .eleventyignore excludes stefankoelle, timecapsule, markdown files
- Deleted: 5 per-site configs, merge script
- Simplified: package.json (single build/dev commands)
- Simplified: GitHub Actions workflow (no matrix, no merge job)
- Fixed: parent links for sub-site detail pages

shared/_includes/sitemap.njk

@@ -1,9 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
-{%- for page in collections.all %}
+{%- set sitemapPages = collections[sitemapCollection] if sitemapCollection else collections.all %}
+{%- for page in sitemapPages %}
   {%- if not page.url.includes("404") %}
   <url>
-    <loc>{{ site.url }}{{ site.pathPrefix | default("") }}{{ page.url }}</loc>
+    <loc>{{ site.url }}{{ pathPrefix }}{{ page.url }}</loc>
     <lastmod>{{ page.date | date }}</lastmod>
     <changefreq>{% if page.url == "/" %}weekly{% else %}monthly{% endif %}</changefreq>
     <priority>{% if page.url == "/" %}1.0{% elif parent %}0.8{% else %}0.7{% endif %}</priority>