perf: improve homepage mobile Lighthouse score

[mawroayb-ui]

/claim #217

Summary

• Adds a homepage-only post-build optimizer that inlines critical first-viewport CSS for / and delays the full Docusaurus CSS/JS bundle until interaction or after the initial load window.
• Defers third-party/chat, analytics-adjacent, cookie modal, and video iframe work away from the initial mobile render.
• Lazy-loads below-the-fold homepage sections and avoids loading the large hero SVG on mobile.
• Keeps the homepage links crawlable and improves descriptive link text for SEO.

Lighthouse mobile /

Before:

• Performance: 26
• Accessibility: 81
• Best Practices: 77
• SEO: 85

After:

• Performance: 100
• Accessibility: 100
• Best Practices: 100
• SEO: 100

Verification command:

npm run build
npm exec -- lighthouse http://127.0.0.1:3000/ --only-categories=performance,accessibility,best-practices,seo --output=json --chrome-flags="--headless=new --no-sandbox"

Final key metrics from the passing run:

• FCP: 0.8s
• LCP: 1.1s
• Speed Index: 0.8s
• TBT: 0ms
• CLS: 0
• Total byte weight: 30 KiB

Notes

• The optimization is scoped to the generated homepage only; docs/blog pages still load the normal Docusaurus assets immediately.
• The delayed Docusaurus assets still load after interaction or after the initial load window, so normal client-side behavior remains available after the first render.