feat: enhance export and import workflows with improved error handling and notifications

static/js/notifications.js

@@ -0,0 +1,38 @@
+(() => {
+  let container;
+
+  function ensureContainer() {
+    if (!container) {
+      container = document.createElement("div");
+      container.className = "toast-container";
+      document.body.appendChild(container);
+    }
+    return container;
+  }
+
+  function show({ message, level = "info", timeout = 5000 } = {}) {
+    const root = ensureContainer();
+    const toast = document.createElement("div");
+    toast.className = `toast toast--${level}`;
+    toast.setAttribute("role", "alert");
+    toast.innerHTML = `
+      <span class="toast__icon" aria-hidden="true"></span>
+      <p class="toast__message">${message}</p>
+      <button type="button" class="toast__close" aria-label="Dismiss">×</button>
+    `;
+    root.appendChild(toast);
+
+    const close = () => {
+      toast.classList.add("hidden");
+      setTimeout(() => toast.remove(), 200);
+    };
+
+    toast.querySelector(".toast__close").addEventListener("click", close);
+
+    if (timeout > 0) {
+      setTimeout(close, timeout);
+    }
+  }
+
+  window.NotificationCenter = { show };
+})();