Convert Markdown to sanitized HTML that is safe to embed directly in a page, email or app. GFM supported: tables, task lists, strikethrough, fenced code. Output passes a strict tag/attribute allowlist: scripts, styles, iframes, event handlers and javascript: URLs are removed; links keep only http(s)/mailto targets, images only http(s) or base64 image data URIs. Send JSON {markdown} or a raw text/markdown body, max 2 MB. Returns {html}.