Generate and edit AI images from Clojure with no API key and no account.

  (require '[kavel.core :as kavel])
  (kavel/generate "a paper boat at sunrise, soft fog, 35mm film")
  ;; => {:url "https://cdn.kavel.ai/uploads/kie/image/....webp" :watermarked? true}

Without a key it calls the anonymous tier of https://www.kavel.ai, so the
first call works on a machine with nothing configured. With :api-key (or the
KAVEL_API_KEY environment variable) every call runs on your account.

Failures throw ex-info whose data carries :reason, one of :quota, :rejected,
:sign-in, :auth, :timeout or :other, so a caller can tell waiting from
rewording from signing in.