* FEATURE: Inline topic summary. Cached version accessible to everyone.
Anons and non-members of the `custom_summarization_allowed_groups_map` groups can see cached summaries for any accessible topic. After the first 12 hours and if the posts to summarize have changed, allowed users clicking on the button will automatically re-generate it.
* Ensure chat summaries work and prevent model hallucinations when there are no messages.
Updates the interface for implementing summarization strategies and adds a cache layer to summarize topics once.
The cache stores the final summary and each chunk used to build it, which will be useful when we have to extend or rebuild it.
