Implement waitlist landing page FRE-656

- Add waitlist tRPC router with signup mutation and count query
- Add referral code generation and tracking
- Register waitlist router in app router
- Add useWaitlistSignup, useWaitlistCount, useReferralCount hooks
- Update landing page with email capture form, live waitlist counter, referral sharing
- Add waitlist and referral CSS styles

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/trpc/index.ts

@@ -2,6 +2,7 @@ import { createHTTPServer } from '@trpc/server/adapters/standalone';
 import { projectRouter } from './project-router';
 import { revisionsRouter } from './revisions-router';
 import { scriptsRouter } from './scripts-router';
+import { waitlistRouter } from './waitlist-router';
 import type { TRPCContext } from './types';
 import type { TRPCError } from '@trpc/server';
 import { t } from './router';
@@ -11,6 +12,7 @@ export const appRouter = t.router({
   project: projectRouter,
   revisions: revisionsRouter,
   scripts: scriptsRouter,
+  waitlist: waitlistRouter,
 } as const);
 
 export type AppRouter = typeof appRouter;