Flutterwave Rate Limits

Reconciled rate-limit and traffic-management posture for the Flutterwave for Business v4 API. Flutterwave does not publish a single global RPS ceiling; limits are dynamic per merchant tier, per endpoint, and are exposed via standard HTTP 429 responses with a `Retry-After` header. The platform handles 20M+ API calls per day in aggregate. The values below are conservative defaults that match observed sandbox behaviour and Flutterwave support guidance for production merchants.