File uploads

Payment proof images are uploaded with chat messages.

Flow

1. singleImage('image') (Multer, memory storage) accepts one file up to 5 MB.
2. upload.service.storeImage sniffs the magic bytes with detectImageType:
   • JPEG FF D8 FF
   • PNG 89 50 4E 47 0D 0A 1A 0A
   • WebP RIFF….WEBP
3. Anything else — SVG, PDF, HTML renamed to .png — is rejected with 400.
4. The image is stored and its URL saved on the message.

The client-provided MIME type is never trusted.

Storage backends

Condition	Backend	URL
CLOUDINARY_URL set	Cloudinary, folder nexlm/payment-proofs	secure_url from Cloudinary
Otherwise	Local disk server/uploads/payment-proofs/	${PUBLIC_API_URL}/uploads/payment-proofs/<random>.<ext>

Local files get a 32-hex-character random name and are served by express.static with a 7-day cache. Helmet's Cross-Origin-Resource-Policy is set to cross-origin so the client on another origin can display them.

Production notes

• Use Cloudinary (or another object store) in production — local disk is ephemeral on most PaaS hosts.
• Payment proofs can contain bank details. Treat upload URLs as sensitive and consider signed/private delivery.