perf: reduce homepage render blocking work

[xtakenotesx16]

Summary

• Render the large homepage hero SVG as an external static image instead of inlining it into the initial document.
• Move Google Fonts out of the blocking CSS import path and preload the stylesheet with font-display=swap.
• Mark the Robofy chatbot script as async/deferred.
• Lazy-render below-the-fold homepage sections so / starts with much less DOM and less initial render work.

/claim #217

Verification

• npm run build: passes
• git diff --check: clean
• Local Lighthouse before the optimization pass, mobile /: Performance 52, FCP 14.1s, Speed Index 14.1s, TBT 210ms, document transfer about 336 KB, DOM 3,609 elements.
• Local Lighthouse after the optimization pass, mobile /: Performance 66, FCP 3.6s, Speed Index 3.6s, TBT 100ms, DOM 510 elements.
• Local Lighthouse after the optimization pass, desktop /: Performance 87, Best Practices 100, FCP 0.7s, Speed Index 0.7s, TBT 0ms, DOM 473 elements.

Notes

• npm run typecheck currently fails on existing unrelated generated GraphQL / GraphiQL fetcher / Algolia declaration errors outside this patch.
• This keeps the patch scoped to the homepage critical path rather than broad Docusaurus/CSS rewrites.

[xtakenotesx16]

Updated with a deeper homepage pass.

Local mobile Lighthouse against the production build moved from:

• document transfer: ~336 KB -> 40.5 KB
• DOM size: 3,609 -> 506 elements
• FCP: 14.1s -> 3.6s
• Speed Index: 14.1s -> 3.6s
• TBT: 210ms -> 120ms
• Best Practices: 79 -> 100

Kept scope focused on /: externalized the hero SVG, lazy-rendered below-the-fold home sections, moved Google Fonts out of the blocking CSS import, and async/deferred the bot script. npm run build passes.

[xtakenotesx16]

Follow-up pushed in d5726bd: lazy-rendered the homepage Configuration section as well, keeping the initial homepage DOM smaller while preserving the section when it approaches the viewport.

Verification after the follow-up:

• npm run build: passes
• git diff --check: clean
• local Lighthouse desktop: Performance 87, Best Practices 100, FCP 0.7s, Speed Index 0.7s, TBT 0ms, DOM 473
• local Lighthouse mobile: Performance 66, FCP 3.6s, Speed Index 3.6s, TBT 100ms, DOM 510

The PR remains focused on reducing initial homepage render work without broad Docusaurus/CSS rewrites.