feat: add proper marketing footer with privacy/terms links

- marketing/components/footer.tsx: multi-column footer with product,
  resources, and legal columns — Privacy Policy clearly linked on homepage
  (satisfies Google OAuth consent screen requirement)
- Replaces thin single-line footer in layout.tsx

Co-authored-by: Cursor <cursoragent@cursor.com>

marketing/components/index.ts

@@ -11,4 +11,5 @@ export { Features } from "./features";
 export { HowItWorks } from "./how-it-works";
 export { Pricing } from "./pricing";
 export { CTA } from "./cta";
+export { Footer } from "./footer";