[xtmhub] Prevent user from seeing 'register'/'unregister' buttons in the demo instance

[jbanety]

Description

In demo mode, the "Register in XTM Hub" and "Unregister from XTM Hub" buttons on the Settings > XTM Hub page are still accessible. These actions should be blocked when the platform is running in demo mode, similar to how the "Unregister" button is already hidden in trial mode.

Environment

1. OS (where OpenCTI server runs): All
2. OpenCTI version: Latest
3. OpenCTI client: Frontend
4. Other environment details: Platform running with platform_demo: true

Reproducible Steps

1. Configure the platform in demo mode (platform_demo: true)
2. Navigate to Settings > Parameters > XTM Hub
3. Observe that the "Register in XTM Hub" button is displayed and clickable
4. (If already registered) Observe that the "Unregister from XTM Hub" button is also displayed and clickable

Expected Output

When the platform is in demo mode, both "Register in XTM Hub" and "Unregister from XTM Hub" buttons should be hidden, preventing any registration or unregistration action.

Actual Output

Both buttons are visible and functional in demo mode, allowing users to trigger the registration/unregistration flow.

Additional information

Related to FiligranHQ/xtm-hub#1784