chore: post-deploy SEO verification (Rich Results, Schema validator, Search Console)

[elfensky]

Summary

Post-deploy SEO verification steps split out from #123, which was closed once all implementation work was complete. These require the production site to be live and reachable by external tooling.

Tasks

• Test with Google Rich Results Test
• Validate JSON-LD with the Schema.org validator
• Check Google Search Console for indexing issues
• Verify SERP preview for the homepage, /archives, and /docs/about

Context

All SEO/meta implementation (per-page metadata exports, JSON-LD via the shared JsonLd component, sitemap, robots.txt, breadcrumbs) was completed under #123. This issue tracks only the manual external-tool verification, now actionable since v0.47.9 is deployed.