Add Lance namespace read/write support

[FANNG1]

Summary

• add a shared Lance namespace resolver for URI-or-namespace validation, namespace client construction, table resolution, and storage option merging
• wire namespace table support through daft.read_lance, DataFrame.write_lance, LanceDataSink, and worker scan reconstruction
• add dir namespace coverage plus a gated Gravitino Lance REST namespace integration test

Validation

• make check-format
• .venv/bin/python -m py_compile daft_lance/namespace.py daft_lance/_lance.py daft_lance/lance_data_sink.py daft_lance/lance_scan.py daft_lance/utils.py tests/io/lancedb/test_namespace_rest_e2e.py
• .venv/bin/python -m pytest tests/io/lancedb/test_namespace.py tests/io/lancedb/test_namespace_rest_e2e.py -v
• DAFT_LANCE_REST_URI=http://127.0.0.1:9101/lance NO_PROXY='' no_proxy='' AWS_ACCESS_KEY_ID=minioadmin AWS_SECRET_ACCESS_KEY=minioadmin AWS_ENDPOINT_URL=http://127.0.0.1:9000 AWS_REGION=us-east-1 AWS_DEFAULT_REGION=us-east-1 AWS_ALLOW_HTTP=true .venv/bin/python -m pytest tests/io/lancedb/test_namespace_rest_e2e.py -v