Fix broken CodeSandbox showcase thumbnails in docs

[Nyx-abu]

Hi everyone,

I noticed that many of the showcase thumbnails in the documentation are currently broken and failing to render. It looks like the CodeSandbox screenshot API is returning a 403 Forbidden error due to Cloudflare protection, which is preventing the images from loading.

To fix this properly without introducing performance regressions (like embedding dozens of live iframes that would exhaust WebGL contexts), I manually captured static screenshots of the 21 remaining CodeSandboxes. I have added them to docs/images/sandboxes and updated the .mdx files to use the screenshot_url prop.

This approach restores the visual showcase for users while keeping the page load fast and reliable.

Let me know if you need any adjustments or have a different preferred approach for this!

[codesandbox-ci]

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Latest deployment of this branch, based on commit bff3639:

Sandbox	Source
example	Configuration

[WestonVincze]

This feels like a solid idea, but the screenshots don't actually show the codesandbox examples. Each screenshot is a codesandbox security verification page where the only difference between them is the id of the project.