Add aria-required to ServiceSelector radiogroup for screen reader clarity

When a continue button is present (selection gates forward progress),
the radiogroup now communicates that a selection is mandatory.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/organisms/ServiceSelector/ServiceSelector.tsx

@@ -109,6 +109,7 @@ export const ServiceSelector = React.forwardRef<HTMLDivElement, ServiceSelectorP
         <Box
           role="radiogroup"
           aria-label={heading}
+          aria-required={continueLabel ? true : undefined}
           sx={{ display: 'flex', flexDirection: 'column', gap: 1.5 }}
         >
           {items.map((item) => (