fix(settings): add optional dashboard shelf sync

Keep dashboard layouts browser-local by default and let users opt in to account storage.
Group library selection and shelf sync in one dropdown, preserve legacy client settings,
and block sync changes for demo-restricted accounts.

Fixes #1646

packages/types/src/auth.ts

@@ -43,6 +43,8 @@ export interface UserSettings {
   notificationPreferences?: import("./notification").NotificationPreferences;
   seriesCollapsePreferences?: import("./series-collapse").SeriesCollapsePreferences;
   dashboardConfig?: import("./dashboard").DashboardConfig;
+  /** Separate from dashboardConfig so legacy clients replacing it preserve shelf preferences. */
+  dashboardShelfConfig?: import("./dashboard").DashboardShelfConfig;
   sidebarConfig?: import("./sidebar").SidebarConfig;
   achievementPreferences?: {
     enabled?: boolean;

packages/types/src/dashboard.ts

@@ -103,6 +103,14 @@ export interface ScrollerConfig {
   smartScopeId?: number;
 }
 
+export type DashboardShelfLayout = "wide" | "two-columns";
+
+export interface DashboardShelfConfig {
+  syncAcrossSessions?: boolean;
+  scrollers?: ScrollerConfig[];
+  shelfLayout?: DashboardShelfLayout;
+}
+
 export const WIDGET_TYPE = {
   READING_STREAK: "reading-streak",
   CURRENTLY_READING: "currently-reading",