Add a comprehensive README describing the Simple File Server project. Documents core features (file/folder management, drag-and-drop, bulk ZIP downloads, previews), UI/UX details (grid/list views, dark mode, breadcrumbs), security/backend (session-based auth, MariaDB), tech stack, project structure, and deployment instructions (Docker Compose and manual Node.js). Includes default credentials (admin/admin) and a recommendation to change them for production.
