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/Progress.tsx

@@ -0,0 +1,33 @@
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface ProgressProps {
+  value: number;
+  max?: number;
+  className?: string;
+  showLabel?: boolean;
+}
+
+const Progress = React.forwardRef<HTMLDivElement, ProgressProps>(
+  ({ value, max = 100, className, showLabel = false }, ref) => {
+    const percentage = Math.min(Math.max((value / max) * 100, 0), 100);
+
+    return (
+      <div ref={ref} className={cn('w-full', className)}>
+        <div className="relative h-4 w-full overflow-hidden rounded-full bg-secondary">
+          <div
+            className="h-full bg-primary transition-all duration-300 ease-in-out"
+            style={{ width: `${percentage}%` }}
+          />
+        </div>
+        {showLabel && (
+          <div className="mt-1 text-xs text-muted-foreground text-right">{Math.round(percentage)}%</div>
+        )}
+      </div>
+    );
+  }
+);
+
+Progress.displayName = 'Progress';
+
+export { Progress };