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

infra/dev-environment/index.njk

@@ -1,7 +1,8 @@
 ---
 title: "Xubuntu Dev VM"
 section: "infra"
-parent: "/"
+tags: "infra"
+parent: "/infra/"
 description: "A disposable, daily-backed-up Xubuntu VM for AI-assisted, remote development via SSH and Chrome Remote Desktop."
 layout: base.njk
 ---