make error toast global in admin routes

src/lib/stores.ts

@@ -4,5 +4,16 @@ import { writable } from 'svelte/store';
 
 export const playAudio: Writable<boolean> = persisted('playAudio', false);
 
+export const errorMessage: Writable<string | null> = (() => {
+	const store: Writable<string | null> = writable(null);
+	return {
+		subscribe: store.subscribe,
+		set: (value) => {
+			if (value != null) store.set(null);
+			store.set(value);
+		},
+		update: store.update
+	};
+})();
 export const reportCount: Writable<number> = writable(0);
 export const adminCount: Writable<number> = writable(0);