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/figlet/TextInput.tsx

@@ -0,0 +1,28 @@
+'use client';
+
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface TextInputProps {
+  value: string;
+  onChange: (value: string) => void;
+  placeholder?: string;
+  className?: string;
+}
+
+export function TextInput({ value, onChange, placeholder, className }: TextInputProps) {
+  return (
+    <div className={cn('relative', className)}>
+      <textarea
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={placeholder || 'Type something...'}
+        className="w-full h-32 px-4 py-3 text-base border border-input rounded-lg bg-background resize-none focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 placeholder:text-muted-foreground"
+        maxLength={100}
+      />
+      <div className="absolute bottom-2 right-2 text-xs text-muted-foreground">
+        {value.length}/100
+      </div>
+    </div>
+  );
+}