feat: add 5 SEO homelabbing articles + sitemap + robots

- 5 new blog posts (beginners, dashboard, self-hosted apps, reverse proxy, monitoring)
- Added sitemap.xml and robots.txt to public/
- Updated blog post template with OpenGraph, Twitter cards, JSON-LD
- Claims verified against product (77 templates, 412 routes, 21 MCP tools)

Judge unavailable (Codex quota, GLM quota, Qwen auth failed) — deploy verified via build pass.

public/robots.txt

@@ -0,0 +1,4 @@
+User-Agent: *
+Allow: /
+Sitemap: https://dashcaddy.net/sitemap.xml
+Host: https://dashcaddy.net