Fix ErrorBoundary to use ka- CSS classes instead of Tailwind

[isaacsight]

src/components/ErrorBoundary.tsx uses Tailwind-style classes (flex-1, items-center, max-w-md, etc.) but the project uses vanilla CSS with ka- prefix. The error boundary fallback UI is likely unstyled/broken. Replace with proper ka- classes.

[isaacsight]

Fixed in 7c7ad6d — ErrorBoundary now uses ka-error-* classes.