refactor: split frontend application features

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/components/actions/errorMessage.ts

@@ -0,0 +1,7 @@
+import { ApiError } from '../../api/client'
+
+export function errorMessage(error: unknown) {
+  return error instanceof ApiError || error instanceof Error
+    ? error.message
+    : 'Something went wrong'
+}