feat: add foreign key constraints and metrics for blockchain node

apps/explorer-web/src/components/notifications.ts

@@ -0,0 +1,34 @@
+const TOAST_DURATION_MS = 4000;
+
+let container: HTMLDivElement | null = null;
+
+export function initNotifications(): void {
+  if (!container) {
+    container = document.createElement("div");
+    container.className = "toast-container";
+    document.body.appendChild(container);
+  }
+}
+
+export function notifyError(message: string): void {
+  if (!container) {
+    initNotifications();
+  }
+  if (!container) {
+    return;
+  }
+
+  const toast = document.createElement("div");
+  toast.className = "toast toast--error";
+  toast.textContent = message;
+  container.appendChild(toast);
+
+  requestAnimationFrame(() => {
+    toast.classList.add("is-visible");
+  });
+
+  setTimeout(() => {
+    toast.classList.remove("is-visible");
+    setTimeout(() => toast.remove(), 250);
+  }, TOAST_DURATION_MS);
+}