Add Stationery and Stationery Dark themes with notebook chrome.

Manila folders, ruled chat, post-it nav, and folder tabs; dark variant uses Catppuccin Mocha colors with muted stickies and soft glows.

src/app/components/nav/NavItem.tsx

@@ -13,6 +13,7 @@ export const NavItem = as<
   <AsNavItem
     className={classNames(css.NavItem({ variant, radii }), className)}
     data-highlight={highlight}
+    data-nav-item=""
     {...props}
     ref={ref}
   >