This update fixes an issue where the AI user preferences tab was not appearing unless `SiteSetting.ai_helper_enabled` was `true`. This is because we previously checked for it's presence when user preferences only had a single setting related to Helper. However, since then, we've also added search discoveries setting there too. As such, we don't want it to depend on Helper. We also sneak in this update a modernization of converting the preferences template from `.hbs` to `.gjs`.
We no longer support the "provider:model" format in the "ai_helper_model" and
"ai_embeddings_semantic_search_hyde_model" settings. We'll migrate existing
values and work with our new data-driven LLM configs from now on.
