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

smarthome/air-quality/index.njk

@@ -1,7 +1,8 @@
 ---
 title: "Air Quality Dashboard"
 section: "smarthome"
-parent: "/"
+tags: "smarthome"
+parent: "/smarthome/"
 description: "Real-time temperature and humidity monitoring across all rooms, powered by InfluxDB and Chart.js."
 layout: base.njk
 ---