PowerPoint转PDF转换器

To enable Cloud Mode:

1. Create backend endpoint: /api/convert/powerpoint-to-pdf
2. Choose conversion method:
   • LibreOffice headless (self-hosted, free)
   • CloudConvert API (paid, easy)
   • ConvertAPI (paid, simple)
3. Update the convertWithAPI() function
4. Handle file upload and response

const { exec } = require('child_process');
app.post('/api/convert/powerpoint-to-pdf', async (req, res) => {
  // Save uploaded file
  // Run: libreoffice --headless --convert-to pdf file.pptx
  // Return PDF
});