v0.23.6

chore(release): bump version to 0.23.6 (#420)

## Summary

- bump workspace / Python package version from `0.23.5` to `0.23.6`
- keep Cargo workspace, Python package, and Commitizen versions aligned
- update workspace package versions in `Cargo.lock`

## Highlights since 0.23.5

- #419 — cache residence TTL histogram, dashboard, and docs
- #418 — fix(connector): hold blocks until all save tasks finish

## Validation

- `cargo metadata --locked --no-deps --format-version 1`
- version consistency for Cargo, Python, and Commitizen metadata (local
equivalent of the CI check)

## Release

After approval and merge, create and push tag `v0.23.6` to trigger the
release workflow.