av: clone broadcastbeat sources + AV Beat rebrand (Phase 1)

- Replaces the prior Rocket scaffold (saved on pre-bb-clone-rollback branch)
- Domain: broadcastbeat.com -> avbeat.com
- Brand: Broadcast Beat -> AV Beat
- Slug: broadcastbeat -> avbeat (package, identifiers)
- Schema fallback: bb -> av (env var name unchanged)
- Placeholder AV BEAT logo (gold->red gradient) at /assets/logos/av.svg
- All BB/RMP logo references repointed

Outstanding before public DNS swap:
  - Supabase av schema bootstrap (mirror of bb tables)
  - WordPress archive import (avbeat-com -> av.articles)
  - Coolify env vars
  - dev-avbeat.onsethost.com staging deploy + visual review

src/app/admin/email/page.tsx

@@ -4,7 +4,7 @@ import Link from 'next/link';
 import { useAuth } from '@/contexts/AuthContext';
 import { useRouter } from 'next/navigation';
 
-const SITES = ['broadcastbeat','avbeat','backlotbeat','broadcastengineering'];
+const SITES = ['avbeat','avbeat','backlotbeat','broadcastengineering'];
 
 function DnsCheck({ label, valid }: { label: string; valid: boolean | null }) {
   return (