Generate images from layer compositions. Layer types: solid-color, gradient, text (with Markdown bold/italic), image, qr-code, barcode (Code 128, EAN-13, EAN-8, Code 39, ITF, Codabar), and layout (nested flex-like container with direction, gap, alignment, and padding). Layers are composited by index order with per-layer opacity and rotation. 99 Google Fonts are built in (Inter, Roboto, OpenSans, Montserrat, Poppins, Outfit, Lato, etc.) -- reference any by name without uploading font files. Custom fonts can be provided as base64. Output formats: PNG (default), JPEG, WebP, TIFF, GIF, AVIF.