feat: add SidebarSeparator component and integrate into documentation layout

- Introduced SidebarSeparator component for improved sidebar organization.
- Updated layout configuration to utilize the new SidebarSeparator in the documentation layout.

surfsense_web/app/docs/sidebar-separator.tsx

@@ -0,0 +1,12 @@
+"use client";
+
+import type { Separator } from "fumadocs-core/page-tree";
+
+export function SidebarSeparator({ item }: { item: Separator }) {
+	return (
+		<p className="inline-flex items-center gap-2 mb-1.5 px-2 mt-6 font-semibold first:mt-0 empty:mb-0">
+			{item.icon}
+			{item.name}
+		</p>
+	);
+}