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/api/contributor/posts/route.ts

@@ -85,7 +85,7 @@ export async function POST(request: NextRequest) {
             headers: { 'Content-Type': 'application/json' },
             body: JSON.stringify({ username: profile.full_name || user.email, term: bannedMatch.term }),
           }).catch(() => {});
-          return NextResponse.json({ blocked: true, error: 'This post could not be submitted. Please contact the editorial team at editor@broadcastbeat.com for assistance.' }, { status: 422 });
+          return NextResponse.json({ blocked: true, error: 'This post could not be submitted. Please contact the editorial team at editor@avbeat.com for assistance.' }, { status: 422 });
         }
         // Soft ban: flag but allow through
         // Will be tagged below