feat(api): align SDK with KSeF API 2.3.0

[smekcio]

Summary

• update SDK compatibility, generated OpenAPI models, and docs for KSeF API 2.3.0
• add InvoiceExportRequest.onlyMetadata support in the SDK and expose it in CLI via ksef export run --only-metadata
• normalize FA_RR (1) 1-1E form code handling to send FA_RR instead of the legacy RR value
• extend regression coverage for the new OpenAPI fields and keep project coverage at 100%

Testing

• python -m pytest --cov=ksef_client --cov-report=term-missing --cov-fail-under=100
• python tools/check_coverage.py --openapi ..\\ksef-docs\\open-api.json --src src/ksef_client/clients

Closes #30