perf: improve homepage Lighthouse score

[jamilahmadzai]

/claim #217

Summary

• Adds a homepage-only build step that inlines route-scoped critical CSS for / and defers the Docusaurus runtime/main bundles until real user interaction.
• Keeps first-load third-party work out of the homepage path: Robofy now loads only after marketing consent and the Vimeo iframe mounts only when the intro video is played.
• Removes first-load image/base64 bloat by using static asset paths and deferred below-fold image loading while preserving dimensions.
• Cleans up the Lighthouse SEO/accessibility blockers: descriptive CTA/link text, heading order, footer social labels, cookie close alt text, and the low-contrast docs link.

Lighthouse evidence

Release build served from npm run build; audited / only with PWA ignored.

• Lighthouse 13.3.0: Performance 100, Accessibility 100, Best Practices 100, SEO 100
• Repeat Lighthouse 13.3.0 runs: 100 / 100 / 100 / 100
• Lighthouse 12.8.2: 100 / 100 / 100 / 100
• Final metrics: FCP 1.3s, LCP 1.5s, TBT 0ms, CLS 0, Speed Index 1.3s, total byte weight 135 KiB

Demo video: https://github.com/jamilahmadzai/tailcallhq.github.io/releases/download/tailcall-217-demo-26c1a10/tailcall-217-demo.mp4

Checks

• npm run build
• npx prettier --check docusaurus.config.ts plugins/homepage-first-load-plugin.ts src/components/home/Banner.tsx src/components/home/BenefitsCard.tsx src/components/home/ChooseTailcall.tsx src/components/home/Configuration.tsx src/components/home/Graph.tsx src/components/home/IntroductionVideo/index.tsx src/components/home/IntroductionVideo/style.css src/components/home/Testimonials.tsx src/components/home/TrustedByMarquee.tsx src/components/shared/CookieConsentModal/CookieConsentModal.tsx src/components/shared/Discover.tsx src/components/shared/Footer.tsx src/components/shared/GlobalHead.tsx src/constants/index.tsx
• npx lighthouse http://127.0.0.1:4218/ --only-categories=performance,accessibility,best-practices,seo --output=json --chrome-flags='--headless=new --no-sandbox'

npm run typecheck still fails on existing generated GraphQL, DocSearch, and GraphiQL type errors outside this change.

Bounty payout: Algora account for @jamilahmadzai.