Rebuild the web landing page to the blueprint spec

Ten dark cinematic sections: fixed glass nav with a hamburger sheet, hero
with the badge/dual CTA/stats bar, a pausable 35mm film-strip marquee, the
live preset tester (5 stocks, HUD, spec bars), the three-knob custom recipe
simulator, the 6-card feature grid, the QR sharing showcase, free-vs-Pro
pricing, reviews + FAQ accordion and the final CTA/footer.

The page owns its palette and its .lp-* styles, so it renders the same in
either workspace theme, and it pulls no CDN: Syne is bundled and the six
sample negatives are vendored (see docker/README.md). Store buttons raise a
toast instead of the old alert(). The now-dead landing CSS and the unused
land.* dictionary keys are gone.

docker/frontend/src/main.tsx

@@ -1,6 +1,7 @@
 import { createRoot } from 'react-dom/client';
 import './styles/tokens.css';
 import './styles/app.css';
+import './styles/landing.css';
 import { ThemeProvider } from './theme/ThemeProvider';
 import { I18nProvider } from './i18n/I18nProvider';
 import { Landing } from './Landing';