Adds fal-ai/kling-image/v3/text-to-image ($0.028/img, native 2K default,
8 aspect ratios) with its image-to-image edit endpoint. The i2i schema
takes a SINGULAR `image_url` string instead of the usual `image_urls`
list, so the catalog gains an `edit_image_param` knob that
_build_fal_edit_payload honors (first source image only); the
edit-contract test now validates whichever image key the entry declares.
Teknium
ae596d805b