This improves the Captain overview by loading reporting metrics and FAQ
stats from separate endpoints. Range changes now refresh only the
metrics, while reopen-rate calculation reuses the resolved conversation
count to avoid redundant database queries.
## What changed
- Split Captain overview metrics and FAQ stats into separate APIs.
- Fetch FAQ stats independently from range-based metrics.
- Reuse resolved conversation totals when calculating reopen rate.
- Skip the reopen query when there are no resolved conversations.
