Add Stargate and Code Analysis landing pages with shared landing kit

[gabrielrangel95]

Summary

Folds the standalone Stargate and Code Analysis product sites (previously separate Next.js repos) into fluttermix.com as /stargate and /code-analysis, and adds both products to the FloatingNavbar products dropdown.

The two source sites were near-identical twins (both ported from this repo's Remix landing page — 19 of 22 files identical after sg-/ca- prefix normalization), so instead of copying them twice the landing pages share one unified kit:

• components/landing/ — shared .lp-* design system (landing.css, single copy of the former 1,291-line stylesheet), motion presets, primitives (LandingButton, Wordmark, SectionHead, HighlightedCode, WaitlistForm) and 9 sections parameterized by a LandingContent config.
• components/landing/stargate/, components/landing/code-analysis/ — per-product content configs, code snippets, and the only two genuinely divergent components each (HeroWindow, OutputsBento), plus a thin client wrapper.
• Per-product accents (violet / cyan) come from html[data-product] CSS token blocks, reusing the existing product-theming mechanism.

Navbar / theming

• Products dropdown now lists Mix, Remix, Stargate, and Code Analysis (new entries show a text label beside their square glyph — proper wordmark assets can be swapped in later).
• Landing-only products hide the Docs link, Version menu, and GitHub icon; a "Join waitlist" link takes the Docs slot.
• data-product handling extended in both the pre-hydration script (layout.jsx) and getActiveProduct, with new accent blocks in globals.css.
• Fonts need no work: both sites already consume the --font-inter / --font-jetbrains-mono vars the root layout provides.

Waitlist API

One parameterized route (/api/waitlist) serves both products with per-product Resend audiences and welcome emails. Degrades gracefully: dev no-op / prod 503 when keys are missing.

New Vercel env vars to configure:

• RESEND_API_KEY
• RESEND_AUDIENCE_ID_STARGATE
• RESEND_AUDIENCE_ID_CODE_ANALYSIS
• RESEND_FROM_EMAIL (optional; per-product defaults otherwise)

Note on zod

zod is pinned to 4.3.6 via a pnpm override: 4.4.3 breaks nextra's Layout prop validation ("expected nonoptional, received undefined at children") and 500s every route.

Verification

• pnpm build passes; /stargate and /code-analysis prerender as static routes; pagefind indexes only docs pages (landing pages also carry data-pagefind-ignore).
• Dev server: all routes 200 (/, /remix, /stargate, /code-analysis, mix/remix docs, examples); both landing pages render full section stacks with correct copy and accents.
• Waitlist API: valid posts → dev no-op 200; invalid email or unknown product → 400.

🤖 Generated with Claude Code

[gabrielrangel95]

Closing as duplicate — #19 (same changes) is the active PR.