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

next.config.mjs

@@ -70,7 +70,7 @@ const nextConfig = {
         destination: 'https://relevantmediaproperties.com/broadcast-beat---media-kit',
         permanent: true,
       },
-      // WordPress admin redirects for broadcastbeat.com (301 permanent)
+      // WordPress admin redirects for avbeat.com (301 permanent)
       {
         source: '/wp-admin',
         destination: '/admin',