chore: uptake denote 0.2.0

[deer]

Uptakes Denote 0.2 and applies a batch of site improvements discovered through real-world usage.

• Bump @denote/core to 0.2.0 — picks up SEO improvements, og:locale, twitter:card fix, theme-color fix, favicon scaffolding, trailing slash normalization, and "Powered by Denote" attribution
• Add seo block (url, description, locale, JSON-LD) with new tagline: "HTTP for Java 25 — virtual threads, structured concurrency, zero magic."
• Add favicon config field and static/favicon.svg (orange "s." mark)
• Add editUrl for GitHub edit links on doc pages
• Bump serve.build version references from 0.1.0 → 0.1.1 in quickstart and installation docs
• Add "Next steps" and "See also" navigation links at the bottom of each doc page