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/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 };