CSS-only loading and success animation

Build a single-file page with a 320x320 stage containing a CSS-only animation: a document icon is "scanned" by a horizontal light bar for about 2 seconds, then the icon morphs or transitions into a check mark inside a circle with a short satisfying pop, then holds. No JavaScript, no SVG animation elements (SVG shapes are fine, animate them with CSS). Loop every 5 seconds. Respect prefers-reduced-motion by showing the final state statically. Provide a caption under the stage that describes the state using CSS only (e.g. via ::after content changes keyed to the same timeline). Return the complete file in one code block.