Improve technical SEO metadata and social sharing previews

[andrewmcodes]

Summary

The site should better support discoverability and sharing.

Problem

• Technical SEO and metadata are likely not fully leveraged

Proposed changes

• Audit and improve:
  • title tags
  • meta descriptions
  • canonical URLs
  • sitemap coverage
  • Open Graph and Twitter metadata
  • JSON-LD structured data for Person and BlogPosting where relevant

Acceptance criteria

• Key pages have unique metadata
• Social previews render cleanly
• Structured data is present where useful