Implement privacy-preserving Usage Stats (daily, bucketed)

The bottom of https://chatgpt.com/share/e/697ece8e-15f8-800d-a34a-2096c2144366 has a detailed description of what to implement oriented at using codex. It probably requires some extra polish before feeding it in (e.g. at the bottom there are explicit file names for new modules), but overall seems to be sensible.