Add version indicator/toggle to A2UI Composer basic catalog

Currently, the basic catalog (/basic-catalog) displays the updated v0.9 component shapes (like the flattened MultiChoice properties), but there is no visual indicator or toggle on the page showing which specification version is currently active.

Link to the basic catalog:
https://a2ui-composer.ag-ui.com/basic-catalog

Since v0.8 is the stable production version and v0.9 introduces structural changes, missing a version badge causes confusion when tracking schema mismatches. Please add a clear version label or selector to the UI.

The basic catalog page is at /basic-catalog; look for the component that renders the catalog UI. Add a version indicator (like a badge or toggle) showing v0.9 vs v0.8. Check how version state is managed (likely in a context or store) and update the UI accordingly. Verify by running the dev server and navigating to the catalog page to see the version label.

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