Implement ability to hide AI features in self-hosted deployment

[dbumblis-parabol]

Issue - Enhancement

With our government customers, we will be deploying into air-gapped environments with no access to openAI and the use of generative AI will be limited / prohibited currently.

Although the AI features in the application do not work, the UI / UX makes it seems like the features are supposed to. We should implement a way to hide the AI Icebreakers and AI meeting summaries from the UI for self-hosted instances. Passing down the value that can be controlled by the operator is probably the most desired way to implement.

Acceptance Criteria (optional)

Users can:

• Set an ENV_VAR to disable / hide AI features
• AI messaging does not appear in the application

Estimated effort: 15 points (see CONTRIBUTING.md)