v0.7.1: pyarrow runtime dependency fix

Bug Fixes

• Python: declare pyarrow as a runtime dependency (#2)
  • pip install qvdrs now auto-installs pyarrow — previously users had to discover the requirement after hitting ModuleNotFoundError: No module named 'pyarrow' on calls like register_duckdb(), read_qvd_to_arrow(), read_qvd_to_pandas(), read_qvd_to_polars(), etc.

New Install Extras

```bash
pip install qvdrs # core + Arrow (pyarrow auto-installed)
pip install "qvdrs[pandas]" # + pandas
pip install "qvdrs[polars]" # + polars
pip install "qvdrs[duckdb]" # + duckdb
pip install "qvdrs[all]" # everything
```

CI

• Added end-to-end Python smoke test that installs the built wheel into a clean venv and exercises register_duckdb* directly. This regression class is now caught before publish.

Migration

No breaking changes.