feat: implement Figlet, Pastel, and Unit tools with a unified layout

- Add Figlet text converter with font selection and history
- Add Pastel color palette generator and manipulation suite
- Add comprehensive Units converter with category-based logic
- Introduce AppShell with Sidebar and Header for navigation
- Modernize theme system with CSS variables and new animations
- Update project configuration and dependencies

components/ui/Separator.tsx

@@ -0,0 +1,32 @@
+'use client';
+
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+const Separator = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement> & {
+    orientation?: 'horizontal' | 'vertical';
+    decorative?: boolean;
+  }
+>(
+  (
+    { className, orientation = 'horizontal', decorative = true, ...props },
+    ref
+  ) => (
+    <div
+      ref={ref}
+      role={decorative ? undefined : 'separator'}
+      aria-orientation={decorative ? undefined : orientation}
+      className={cn(
+        'shrink-0 bg-border',
+        orientation === 'horizontal' ? 'h-[1px] w-full' : 'h-full w-[1px]',
+        className
+      )}
+      {...props}
+    />
+  )
+);
+Separator.displayName = 'Separator';
+
+export { Separator };