Upgrade frontend to Node 26, React 19, Vite 8, Apollo Client 4 and ESLint 10

frontend/src/contexts/ToastContext.ts

@@ -0,0 +1,22 @@
+import React from "react";
+
+export type Background = "primary" | "danger";
+
+export interface ToastProps {
+  visible: boolean;
+  message: string;
+  showToast: (message: string, background?: Background) => void;
+  hide: () => void;
+  background: Background;
+}
+
+export const defaultToastState: ToastProps = {
+  // FIXME: revert
+  visible: false,
+  message: "",
+  showToast: () => {},
+  hide: () => {},
+  background: "primary",
+};
+
+export const ToastContext = React.createContext<ToastProps>(defaultToastState);