feat(mui): ConfirmDialog processing text 'Zpracovávám…' + re-wire Users delete loading

After clicking the confirm button, it shows 'Zpracovávám…' (disabled) while the action is in flight — matching how the form modal shows 'Ukládám…'. The earlier freeze keeps it through the close fade (no flash back to the confirm label).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/Users.tsx

@@ -479,6 +479,7 @@ export default function Users() {
         }
         confirmText="Smazat"
         confirmVariant="danger"
+        loading={deleteUser.isPending}
       />
     </Box>
   );