Relax contrast naming limitations for R1 files import

When trying to import an R1 project, it can fail based on duplicate contrast names. This should not really matter, and we should relax this constraint (probably at the pyRAT level?)....

<img width="470" height="281" alt="Image" src="https://github.com/user-attachments/assets/88bdcb0d-96b6-4ada-bda0-143216e3d277" />