feat: Initialize frontend with React, Vite, and Tailwind CSS

- Set up main entry point for React application.
- Create About, Home, NotFound, Privacy, and Terms pages with SEO support.
- Implement API service for file uploads and task management.
- Add global styles using Tailwind CSS.
- Create utility functions for SEO and text processing.
- Configure Vite for development and production builds.
- Set up Nginx configuration for serving frontend and backend.
- Add scripts for cleanup of expired files and sitemap generation.
- Implement deployment script for production environment.

frontend/public/robots.txt

@@ -0,0 +1,6 @@
+# robots.txt — SaaS-PDF
+User-agent: *
+Allow: /
+Disallow: /api/
+
+Sitemap: https://yourdomain.com/sitemap.xml