feat: initialize Convert UI - browser-based file conversion app

- Add Next.js 16 with Turbopack and React 19
- Add Tailwind CSS 4 with OKLCH color system
- Implement FFmpeg.wasm for video/audio conversion
- Implement ImageMagick WASM for image conversion
- Add file upload with drag-and-drop
- Add format selector with fuzzy search
- Add conversion preview and download
- Add conversion history with localStorage
- Add dark/light theme support
- Support 22+ file formats across video, audio, and images

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

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

components/ui/Input.tsx

@@ -0,0 +1,28 @@
+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-10 w-full rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background',
+          'file:border-0 file:bg-transparent file:text-sm file:font-medium',
+          'placeholder:text-muted-foreground',
+          'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2',
+          'disabled:cursor-not-allowed disabled:opacity-50',
+          className
+        )}
+        ref={ref}
+        {...props}
+      />
+    );
+  }
+);
+
+Input.displayName = 'Input';
+
+export { Input };