chore: purge shadcn from codebase. Replace with bits-ui components and other tools

src/shared/ui/SidebarContainer/SidebarContainer.svelte

@@ -4,7 +4,7 @@
 -->
 <script lang="ts">
 import type { ResponsiveManager } from '$shared/lib';
-import { cn } from '$shared/shadcn/utils/shadcn-utils';
+import clsx from 'clsx';
 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={cn(
+        class={clsx(
             'shrink-0 z-30 h-full relative',
             'overflow-hidden',
             'will-change-[width]',