test: drive the Lance namespace with LanceDB

The Iceberg catalog is checked against Spark, Trino, ClickHouse, Doris,
Dremio and RisingWave. The Lance one had only its own reference client,
which is the same thing as checking it against ourselves.

LanceDB connects with connect_namespace("rest", ...), which speaks the
routes this catalog implements, so the suite exercises the protocol rather
than our idea of it: list the catalog, open a table through it, read the
schema, run a vector search and a filtered scan, create a table, and read
the same dataset straight off its URI with no catalog at all.

    table_names -> ['lancedb-p0guidmm$ml$embeddings']
    open_table  -> 64 rows
    search      -> [1, 0, 2]
    create_table -> 4 rows, listed by the catalog
    direct read without the catalog -> 64 rows

Seeding is pylance, because the namespace records where a table lives and
does not carry its data. That split is the design rather than a limit of
the test.

One interop note the test encodes: a gateway without STS vends
storage_options carrying an endpoint and a region but no credentials, and
LanceDB uses what the namespace vends on some paths. The container gets
credentials in its environment as well, which is what a deployment without
STS would do.

Claude-Session: https://claude.ai/code/session_01Rkp1Mw5E89Jp6dzJFYiMrm

test/s3tables/catalog_lancedb/Dockerfile.client

@@ -0,0 +1,15 @@
+# LanceDB client for the SeaweedFS Lance Namespace integration test.
+#
+# The Iceberg suites point Spark, Trino and ClickHouse at the catalog; this is
+# the same idea for Lance. LanceDB connects with connect_namespace("rest", ...),
+# which speaks the routes this catalog implements, so what it exercises is the
+# protocol rather than requests we wrote ourselves.
+FROM python:3.11-slim
+
+WORKDIR /app
+
+RUN pip install --no-cache-dir lancedb lance-namespace pylance pyarrow
+
+COPY lancedb_ops.py /app/
+
+CMD ["python3", "/app/lancedb_ops.py", "--help"]