feat(Skeleton): create skeleton component and integrate it into FontVirtualList

src/shared/ui/Skeleton/Skeleton.svelte

@@ -0,0 +1,27 @@
+<!--
+    Component: Skeleton
+    Generic loading placeholder with shimmer animation.
+-->
+<script lang="ts">
+import { cn } from '$shared/shadcn/utils/shadcn-utils';
+import type { HTMLAttributes } from 'svelte/elements';
+
+interface Props extends HTMLAttributes<HTMLDivElement> {
+    /**
+     * Whether to show the shimmer animation
+     */
+    animate?: boolean;
+}
+
+let { class: className, animate = true, ...rest }: Props = $props();
+</script>
+
+<div
+    class={cn(
+        'rounded-md bg-gray-100/50 backdrop-blur-sm',
+        animate && 'animate-pulse',
+        className,
+    )}
+    {...rest}
+>
+</div>