Step 5: add pvserver integration

### 📝 Description of the feature

Now that remote rendering is enabled, add pvserver. The remote rendering configuration should use the pvserver on the backend to do the rendering instead of OpenGL

### Acceptance Criteria

User can start VISOR in remote rendering. It looks and behaves exactly as at the end of Phase 4.

The Theia package is now significantly larger as it contains the pvserver library

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_

Start from the existing remote-rendering configuration and the Theia package/build setup, then trace where backend rendering currently uses OpenGL. Integrate the pvserver library there and verify that VISOR starts in remote-rendering mode, behaves as it did at the end of Phase 4, and produces a larger Theia package containing pvserver.

Written by the indexing model from the issue text.