feat(site): landing-only on www, app gated to demo subdomain (#20)

* feat(site): landing-only on www host, app gated to demo subdomain

- RequireAppHost redirects app routes to / on non-demo hosts
- Signup CTAs swapped for launch-notification mailto on www
- Pricing marked as indicative pre-launch, no subscription purchasable
- SEO: OG/Twitter cards, og.png, JSON-LD, robots.txt, sitemap.xml,
  per-route document titles, SPA rewrite for Vercel

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* chore: ignore vercel link artifacts

Authored By: TDvorak <[email protected]>

* docs: document www/demo host split in deployment targets

Authored By: TDvorak <[email protected]>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

README.md

@@ -6,7 +6,10 @@ billing machinery underneath.
 
 Deployment targets:
 
-- frontend on Vercel
+- frontend on Vercel — `bookra-frontend` serves `www.bookra.eu` (landing only,
+  pre-launch: signup CTAs are mailto and app routes redirect to `/`);
+  `bookrademo` serves `demo.bookra.eu` (full app). The split is enforced by
+  hostname in `apps/frontend/src/lib/app-host.ts`.
 - backend on Railway
 - Neon Postgres + Neon Auth
 - Stripe billing (checkout, customer portal, webhooks, SMS usage invoices)