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/Select.tsx

@@ -0,0 +1,39 @@
+'use client';
+
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface SelectProps extends React.SelectHTMLAttributes<HTMLSelectElement> {
+  label?: string;
+}
+
+const Select = React.forwardRef<HTMLSelectElement, SelectProps>(
+  ({ className, label, children, ...props }, ref) => {
+    return (
+      <div className="space-y-2">
+        {label && (
+          <label htmlFor={props.id} className="text-sm font-medium">
+            {label}
+          </label>
+        )}
+        <select
+          className={cn(
+            'flex h-10 w-full rounded-xl border border-white/10 bg-white/5 px-3 py-2',
+            'text-sm ring-offset-background',
+            'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 focus-visible:border-primary/50',
+            'disabled:cursor-not-allowed disabled:opacity-50 transition-all duration-200',
+            className
+          )}
+          ref={ref}
+          {...props}
+        >
+          {children}
+        </select>
+      </div>
+    );
+  }
+);
+
+Select.displayName = 'Select';
+
+export { Select };