feat: implement core figlet converter with live preview

Implemented Phases 2-4 of the implementation plan:

**Phase 2: Font Management System**
- Created font loading service with caching
- Added API route to list all 373 figlet fonts
- Implemented font metadata types

**Phase 3: Core Figlet Engine**
- Built figlet.js wrapper service for ASCII art generation
- Added async/sync rendering methods
- Implemented debounced text updates (300ms)
- Created utility functions (cn, debounce)

**Phase 4: Main UI Components**
- Built reusable UI primitives (Button, Input, Card)
- Created TextInput component with character counter (100 char limit)
- Implemented FontPreview with loading states
- Added FontSelector with real-time search
- Built main FigletConverter orchestrating all components

**Features Implemented:**
- Live preview with 300ms debounce
- 373 fonts from xero/figlet-fonts collection
- Fuzzy font search
- Copy to clipboard
- Download as .txt file
- Responsive 3-column layout (mobile-friendly)
- Character counter
- Loading states
- Empty states

**Tech Stack:**
- Next.js 16 App Router with Turbopack
- React 19 with client components
- TypeScript with strict types
- Tailwind CSS 4 for styling
- figlet.js for rendering
- Font caching for performance

The application is fully functional and ready for testing!

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/ui/Button.tsx

@@ -0,0 +1,37 @@
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface ButtonProps extends React.ButtonHTMLAttributes<HTMLButtonElement> {
+  variant?: 'default' | 'secondary' | 'outline' | 'ghost';
+  size?: 'default' | 'sm' | 'lg' | 'icon';
+}
+
+const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
+  ({ className, variant = 'default', size = 'default', ...props }, ref) => {
+    return (
+      <button
+        className={cn(
+          'inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-colors focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:pointer-events-none disabled:opacity-50',
+          {
+            'bg-primary text-primary-foreground shadow hover:bg-primary/90': variant === 'default',
+            'bg-secondary text-secondary-foreground shadow-sm hover:bg-secondary/80': variant === 'secondary',
+            'border border-input bg-background shadow-sm hover:bg-accent hover:text-accent-foreground': variant === 'outline',
+            'hover:bg-accent hover:text-accent-foreground': variant === 'ghost',
+          },
+          {
+            'h-9 px-4 py-2': size === 'default',
+            'h-8 rounded-md px-3 text-xs': size === 'sm',
+            'h-10 rounded-md px-8': size === 'lg',
+            'h-9 w-9': size === 'icon',
+          },
+          className
+        )}
+        ref={ref}
+        {...props}
+      />
+    );
+  }
+);
+Button.displayName = 'Button';
+
+export { Button };

components/ui/Card.tsx

@@ -0,0 +1,50 @@
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+const Card = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div
+      ref={ref}
+      className={cn('rounded-xl border bg-card text-card-foreground shadow', className)}
+      {...props}
+    />
+  )
+);
+Card.displayName = 'Card';
+
+const CardHeader = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('flex flex-col space-y-1.5 p-6', className)} {...props} />
+  )
+);
+CardHeader.displayName = 'CardHeader';
+
+const CardTitle = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('font-semibold leading-none tracking-tight', className)} {...props} />
+  )
+);
+CardTitle.displayName = 'CardTitle';
+
+const CardDescription = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('text-sm text-muted-foreground', className)} {...props} />
+  )
+);
+CardDescription.displayName = 'CardDescription';
+
+const CardContent = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('p-6 pt-0', className)} {...props} />
+  )
+);
+CardContent.displayName = 'CardContent';
+
+const CardFooter = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
+  ({ className, ...props }, ref) => (
+    <div ref={ref} className={cn('flex items-center p-6 pt-0', className)} {...props} />
+  )
+);
+CardFooter.displayName = 'CardFooter';
+
+export { Card, CardHeader, CardFooter, CardTitle, CardDescription, CardContent };

components/ui/Input.tsx

@@ -0,0 +1,23 @@
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface InputProps extends React.InputHTMLAttributes<HTMLInputElement> {}
+
+const Input = React.forwardRef<HTMLInputElement, InputProps>(
+  ({ className, type, ...props }, ref) => {
+    return (
+      <input
+        type={type}
+        className={cn(
+          'flex h-9 w-full rounded-md border border-input bg-transparent px-3 py-1 text-base shadow-sm transition-colors file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50 md:text-sm',
+          className
+        )}
+        ref={ref}
+        {...props}
+      />
+    );
+  }
+);
+Input.displayName = 'Input';
+
+export { Input };