feat: persist account group display order and backup preferences

apps/web/src/group-order.ts

@@ -0,0 +1,8 @@
+// Only present groups are displayed; saved groups absent from this view stay private.
+export function orderedGroups(groups: string[], order: string[] = []) {
+  const present = new Set(groups);
+  return [...order.filter((g) => present.delete(g)), ...present];
+}
+export function mergeGroupOrder(visible: string[], saved: string[]) {
+  return [...visible, ...saved.filter((g) => !visible.includes(g))];
+}