feat(12-02): add bg-surface-container text-on-surface to select element in FieldRenderer

- Added bg-surface-container and text-on-surface semantic token classes to select element className
- Fixes select dropdown invisible text in dark mode (browser-applied white background)
- 204 tests pass, zero regressions

src/components/ui/FieldRenderer.tsx

@@ -67,7 +67,7 @@ export function FieldRenderer({ field, register, error }: FieldRendererProps) {
         <select
           id={field.key}
           className={[
-            'w-full rounded-md border px-3 py-2 text-sm focus:outline-none focus-visible:ring-2',
+            'w-full rounded-md border px-3 py-2 text-sm bg-surface-container text-on-surface focus:outline-none focus-visible:ring-2',
             error ? 'border-error focus:ring-error/50' : 'border-outline focus:ring-primary/50',
           ].join(' ')}
           {...register(field.key)}