Display "feature not available" if feature flag is false

[Steve-Mcl]

part three of three

Description

Permits the project nodes to be loaded if broker settings are set but do not connect or attempt to connect to platform. Also, makes it clear to user that the project link feature is not available for their team.

Related Issue(s)

https://github.com/FlowFuse/flowfuse/issues/3560

Checklist

• [x] I have read the contribution guidelines
• [ ] Suitable unit/system level tests have been added and they pass
• [ ] Documentation has been updated
  • [ ] Upgrade instructions
  • [ ] Configuration details
  • [ ] Concepts
• [ ] Changes flowforge.yml?
  • [ ] Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • [ ] Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• [ ] Backport needed? -> add the backport label
• [ ] Includes a DB migration? -> add the area:migration label