Migrate ThemeProvider from Polaris React

Polaris web components have no ThemeProvider equivalent. Their appearance comes from the Shopify admin shell and the loaded Polaris web-components library, not from an app-owned wrapper.

Anchor to Remove the wrapperRemove the wrapper

Render migrated descendants directly and delete ThemeProvider once nothing still depends on its React context. Keep unrelated app context providers that continue to own application behavior.

Migrate theme-dependent custom CSS separately. Replace Polaris React token references with supported app styling, and verify contrast and behavior in Shopify admin rather than recreating a per-subtree Polaris theme.

Don't remove @shopify/polaris while another component still imports it. Test the workflows that used the wrapper, including overlays and focus behavior, before removing the package-level setup.