Improve clusters and several bug fixes

[dsmilkov]

https://huggingface.co/spaces/lilacai/daniel_staging

Clustering (backend):

• Lower min_cluster_size to 5 for the categories, so we can have more coherent categories
• Add timeout of 7 sec (99%-tile response latency for OpenAI is like 3-4 sec) to avoid the 10min timeout. We can now title clusters of 1M docs (11k clusters) in 8mins.
• Disable internal OpenAI retries (we used to have double retries)
• Replace "request" with "snippet" in the prompt to avoid biasing towards user's requests -- improves forum/email/text clustering

UI

• make the histograms reactive to the currently selected group in "group by"
• make pivot reactive to searches (e.g. keyword search, metadata search)
• remember the schema and nav bar state when flipping between cluster view and item view
• Fix a bug with search box state, after page refresh