Dental Imaging Workflow System

1. Implement Token-Based File URL Protection

Each dicom_path and stl_path must be transformed like example:
/secure-file?path=/dicoms/pat001/case001/study123/&token=<signed-token>

The signed token must contain:
------------------------------
user_id ,path, expiry time (e.g., 10 minutes), digital signature (HMAC SHA256)

a) Write a function to generate signed URL:
generateSecureUrl(filePath, userId)

b) Create new API /secure-file

Validate path and token

Ensure:

Token not expired

Token path and request path match

Token is generated for specific user

c) Prevent:

Direct access to /dicoms/... (disable public access)

Directory traversal attacks (../..)