Fix web origin and CORS config for LAN hosting

infra/.env.example

@@ -3,6 +3,7 @@ LIVEKIT_API_SECRET=devsecretdevsecretdevsecretdevsecret
 
 PUBLIC_LIVEKIT_URL=ws://localhost:7880
 PUBLIC_API_URL=http://localhost:8080
+PUBLIC_WEB_URL=http://localhost:3000
 
 SESSION_SECRET=change-me-to-a-long-random-string
 SESSION_TTL_HOURS=12