docs: align SDK docs and CLI tests with KSeF API 2.2.1

[smekcio]

Summary

• update declared SDK compatibility from KSeF API 2.2.0 to 2.2.1
• add explicit RR 1-1E form code example in the docs
• add CLI integration coverage for custom RR form code overrides
• document that the _metadata.json fix in 2.2.1 is upstream/server-side and does not change SDK runtime logic

Testing

• .\.venv\Scripts\python.exe -m pytest tests/cli/integration/test_send_online.py tests/cli/integration/test_send_batch.py

Closes #27