svelte refactor

frontend/src/lib/utils/errors.ts

@@ -0,0 +1,15 @@
+/** Error-handling helpers shared across pages and components. */
+import { ui } from '$lib/stores/ui.svelte';
+
+/** Normalise an unknown thrown value into a human-readable message. */
+export function errorMessage(e: unknown): string {
+	return e instanceof Error ? e.message : String(e);
+}
+
+/**
+ * Raise an error toast for a caught value — the canonical catch-block handler.
+ * Replaces the repeated `ui.notify(e instanceof Error ? e.message : String(e), 'error')`.
+ */
+export function errorToast(e: unknown): void {
+	ui.notify(errorMessage(e), 'error');
+}