docs: read Enterprise connection settings from the shared variables

The Enterprise connection examples now read the database URI from
LANCEDB_URI and the endpoint from LANCEDB_HOST_OVERRIDE, with the API
key and region beside them, the convention the rest of the site uses.
Without an endpoint they stop rather than fall back to one. Their tests
check both.

The REST API reference used LANCEDB_URI for the HTTP endpoint and listed
and created tables at routes the server does not serve. It now uses
LANCEDB_HOST_OVERRIDE, lists tables at /v1/table/, creates `words` from
an Arrow IPC stream, and describes it to confirm the write.

docs/web/basics/connect.mdx

@@ -80,12 +80,12 @@ In Rust, pass the same URI to `connect`.
 
 A `db://` URI connects to a deployment, which runs each operation for you. Get
 the database URI, API key, region and endpoint from the deployment's
-administrator, and pass the endpoint as `host_override`. Keep the API key in a
-secret manager or the environment rather than in source.
+administrator. These examples read them from `LANCEDB_URI`, `LANCEDB_API_KEY`,
+`LANCEDB_REGION` and `LANCEDB_HOST_OVERRIDE`, which keeps the API key out of
+source, and pass the endpoint as `host_override`.
 
 <CodeGroup>
     <CodeBlock filename="Python" language="Python" icon="python">
-    { "import lancedb\n\n" }
     {PyConnectEnterpriseQuickstart}
     </CodeBlock>