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/ai/article-suggestions/route.ts

@@ -22,7 +22,7 @@ export async function POST(request: NextRequest) {
       date: a.date,
     }));
 
-    const systemPrompt = `You are a personalized content recommendation engine for Broadcast Beat, a broadcast engineering news platform.
+    const systemPrompt = `You are a personalized content recommendation engine for AV Beat, a broadcast engineering news platform.
 Given a reader's topic interests and reading history, select the 4 most relevant articles from the provided article list.
 Return ONLY a valid JSON array of slugs in order of relevance. Example: ["slug-1","slug-2","slug-3","slug-4"]
 Do not include any explanation or markdown — only the raw JSON array.`;