feat: add demo mode feature flag using Redacted Script font

packages/web/src/lib/demo.ts

@@ -0,0 +1,10 @@
+const DEMO_KEY = "openconcho:demo";
+
+export function getDemoMode(): boolean {
+	return localStorage.getItem(DEMO_KEY) === "true";
+}
+
+export function applyDemoMode(enabled: boolean): void {
+	document.documentElement.setAttribute("data-demo", String(enabled));
+	localStorage.setItem(DEMO_KEY, String(enabled));
+}