This PR addresses the effort to use one icon representing discourse-ai.
Removed discourse-sparkles from discourse-ai, now included in core ``vendor/assets/svg-icons/discourse-additional.svg``
Besides updating the connector using the new tracking preference service interface, this PR fixes a bug where due to `ai_embeddings_semantic_related_topics_enabled` not having `client: true` the initializer never ran, and we didn't show the related topics list when scrolling to the bottom of a long topic.
David Taylor
Ty Correll
Roman Rizzi