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/public/posts/route.ts

@@ -35,7 +35,7 @@ export async function GET(request: Request) {
 
   // Decorate + reorder so premium and current-advertiser stories surface
   // at the top of the feed.
-  const decorated = await decorateHomepageFeed("broadcastbeat", base);
+  const decorated = await decorateHomepageFeed("avbeat", base);
   const payload = decorated.map((d) => ({
     ...d.article,
     promoted_kind: d.promoted_kind,