feat: add cryptographic utilities and types for secure data handling

webapp/src/components/ToastHost.tsx

@@ -0,0 +1,23 @@
+import type { ToastMessage } from '@/lib/types';
+
+interface ToastHostProps {
+  toasts: ToastMessage[];
+  onClose: (id: string) => void;
+}
+
+export default function ToastHost({ toasts, onClose }: ToastHostProps) {
+  if (!toasts.length) return null;
+  return (
+    <ul className="toast-stack">
+      {toasts.map((toast) => (
+        <li key={toast.id} className={`toast-item ${toast.type}`}>
+          <div className="toast-text">{toast.text}</div>
+          <button type="button" className="toast-close" onClick={() => onClose(toast.id)}>
+            x
+          </button>
+          <div className="toast-progress" />
+        </li>
+      ))}
+    </ul>
+  );
+}