feat: replace clsx with cn util

src/shared/ui/SidebarContainer/SidebarContainer.svelte

@@ -4,7 +4,7 @@
 -->
 <script lang="ts">
 import type { ResponsiveManager } from '$shared/lib';
-import clsx from 'clsx';
+import { cn } from '$shared/lib';
 import type { Snippet } from 'svelte';
 import { getContext } from 'svelte';
 import { cubicOut } from 'svelte/easing';
@@ -79,7 +79,7 @@ function close() {
         The inner div stays w-80 so Sidebar layout never reflows mid-animation.
     -->
     <div
-        class={clsx(
+        class={cn(
             'shrink-0 z-30 h-full relative',
             'overflow-hidden',
             'will-change-[width]',