Refresh the free-tier demo and paid preview

[sergei-argutin]

What changed

• refresh the vendored 400-exercise free bundle and flat WebP assets
• include the paid-tier sample stills alongside the looping animation
• move the Standard-tier preview above the catalog
• version asset URLs from generated_at so refreshed images cannot remain stuck in Next's image cache
• keep only actual looping WebPs in the paid preview gallery

Why

The example was using an older snapshot, the paid-tier promotion sat below all 400 cards, and unchanged asset paths allowed stale thumbnails to remain visible after a bundle refresh.

Validation

• npm run build
• production build generated all 404 routes successfully
• local browser verification confirmed the preview appears before filters and card URLs carry the bundle version

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 94480107b2

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Preserve lazy loading for catalog thumbnails

When the unfiltered catalog renders all 400 exercises, replacing next/image with a plain <img> without loading="lazy" removes the previous component's default lazy loading. The browser can therefore request all 394 unique thumbnail assets—about 6.2 MiB—and decode hundreds of offscreen images on every initial visit, substantially increasing network usage and memory pressure. Add native lazy loading (and preferably asynchronous decoding) or retain the optimized image component with supported cache versioning.

Useful? React with 👍 / 👎.