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

supabase/functions/send-contributor-invite/index.ts

@@ -20,7 +20,7 @@ serve(async (req) => {
       throw new Error("RESEND_API_KEY is not set");
     }
 
-    const acceptUrl = `${siteUrl || "https://broadcastbeat.com"}/invite/accept?token=${token}`;
+    const acceptUrl = `${siteUrl || "https://avbeat.com"}/invite/accept?token=${token}`;
 
     const roleLabel = role === "editor" ? "Editor" : role === "admin" ? "Administrator" : "Contributor";