Add inline Figma and Loom embeds in the editor

[hrescak]

Summary

The editor currently recognizes Figma and Loom URLs and renders them as link cards that open in a new tab. It would be a much better experience to render them as inline embeds (iframes) directly in the post, so readers can preview Figma designs and watch Loom recordings without leaving Draftboard.

Current behavior

• Figma attachments render as a styled card with the Figma logo, filename, and an external-link icon.
• Loom attachments render as a styled card with a play icon, filename, and an external-link icon.
• Both open the original URL in a new browser tab on click.

Relevant code: src/components/editor/nodes/AttachmentNode.tsx (the FIGMA and LOOM branches of AttachmentComponent).

Proposed behavior

• Figma: Render an <iframe> using Figma's embed URL format (https://www.figma.com/embed?embed_host=draftboard&url=<encoded-url>). Show the interactive Figma preview inline in the post.
• Loom: Render an <iframe> using Loom's embed URL format (https://www.loom.com/embed/<video-id>). Show the Loom video player inline in the post.
• Both embeds should be responsive (e.g. 16:9 aspect ratio) and respect the editor's max width.
• Keep the external-link icon / "Open in Figma/Loom" affordance as a small overlay or caption for users who want the full experience.
• In edit mode, consider showing a placeholder or reduced-interactivity version to avoid iframe focus conflicts with the editor.

Implementation notes

• The AttachmentNode already has the FIGMA and LOOM types and the original URL — the main work is in the render function of AttachmentComponent.
• URL parsing helpers (isFigmaUrl, isLoomUrl) already exist in src/lib/utils.ts.
• May need a helper to extract the Loom video ID from share URLs and convert Figma URLs to embed format.
• Consider CSP (frame-src) implications if a Content-Security-Policy header is set.