// TODO: Implement tower-based rate limiting middleware
//
// Approach options:
//   1. Use tower::limit::RateLimitLayer for simple fixed-window rate limiting
//   2. Use governor crate for more sophisticated token-bucket / sliding-window limiting
//   3. Build a custom tower::Layer + tower::Service that reads client IP + license tier
//      and applies different rate limits per tier
//
// Requirements:
//   - Per-IP rate limiting for unauthenticated endpoints (login, register)
//   - Per-license rate limiting for authenticated API endpoints
//   - Higher limits for premium license tiers
//   - Return 429 Too Many Requests with Retry-After header
//
// Example integration:
//   let rate_limit = RateLimitLayer::new(100, Duration::from_secs(60));
//   Router::new().route("/api/...", get(handler)).layer(rate_limit)
