Generate YouTube thumbnails with AI image models (GPT Image, Nano Banana, FLUX, Seedream, Ideogram, Grok) side by side. Optional query: models (comma-separated ids from https://thumbnailcreator.ai/llms.txt), n (1-4 per model), format (16:9, 1:1, 9:16, 4:5). Body: {"prompt": "3-2000 characters"}. Charged only when every image succeeds.