Drag & Drop File Upload with Image Preview (Native Drag and Drop API)

A drag-and-drop image upload zone built with the native HTML5 Drag and Drop API and the File API - no library required. Drop files or click to browse (the zone is a wrapped around a hidden file input, so it's keyboard and screen-reader friendly). Each accepted image gets an instant thumbnail via URL.createObjectURL, a filename/size caption, and a remove button; object URLs are revoked on removal to avoid memory leaks.