feat: add color variables and use them acros the project

src/shared/ui/Skeleton/Skeleton.stories.svelte

@@ -30,7 +30,7 @@ const { Story } = defineMeta({
     }}
 >
     <div class="flex flex-col gap-4 p-4 w-full">
-        <div class="flex flex-col gap-2 p-4 border rounded-xl border-gray-200/50 bg-white/40">
+        <div class="flex flex-col gap-2 p-4 border rounded-xl border-border-subtle bg-background-40">
             <div class="flex items-center justify-between mb-4">
                 <Skeleton class="h-8 w-1/3" />
                 <Skeleton class="h-8 w-8 rounded-full" />

src/shared/ui/Skeleton/Skeleton.svelte

@@ -18,7 +18,7 @@ let { class: className, animate = true, ...rest }: Props = $props();
 
 <div
     class={cn(
-        'rounded-md bg-gray-100/50 backdrop-blur-sm',
+        'rounded-md bg-background-subtle/50 backdrop-blur-sm',
         animate && 'animate-pulse',
         className,
     )}