docs(python): fix Azure storage options examples (#3899)

## Summary

- document that Azure Blob Storage credentials can be passed directly
through `storage_options`
- provide valid quoted `account_name` and `account_key` examples for
both sync and async Python connections
- execute the option dictionaries during doctests so the original
unquoted-key mistake is caught

## Root cause

The historical Python storage guide used `account_name` and
`account_key` as bare identifiers in dictionary literals. Following that
example either raised `NameError` or, when those names were predefined,
produced incorrect option keys. The runtime already accepts direct Azure
credentials, but the current Python API reference did not contain a
corrected Azure example.

## Validation

- `python/.venv/bin/ruff format --check
python/python/lancedb/__init__.py`
- `python/.venv/bin/ruff check .`
- `cd python && uv run --no-sync pytest --doctest-modules
python/lancedb/__init__.py -q`
- `cd python && uv run --no-sync pytest python/tests/test_import.py -q`

Fixes #2236

<!-- lance-gatekeeper-fix:v1 agent=7a7a9e009eb2ebe52ac9b1adf2e8afb2
generation=1 -->

Co-authored-by: Gatefixer <313497061+lancedb-gatefixer[bot]@users.noreply.github.com>
Co-authored-by: Xuanwo <github@xuanwo.io>

python/python/lancedb/__init__.py

@@ -179,6 +179,18 @@ def connect(
     ...     },
     ... )
 
+    For Azure Blob Storage, credentials can be passed directly without setting
+    environment variables:
+
+    >>> azure_storage_options = {
+    ...     "account_name": "some-account",
+    ...     "account_key": "some-key",
+    ... }
+    >>> db = lancedb.connect(  # doctest: +SKIP
+    ...     "az://my-container/my-database",
+    ...     storage_options=azure_storage_options,
+    ... )
+
     For tests and temporary data, use an in-memory database:
 
     >>> db = lancedb.connect("memory://")
@@ -465,6 +477,10 @@ async def connect_async(
     --------
 
     >>> import lancedb
+    >>> azure_storage_options = {
+    ...     "account_name": "some-account",
+    ...     "account_key": "some-key",
+    ... }
     >>> async def doctest_example():
     ...     # For a local directory, provide a path to the database
     ...     db = await lancedb.connect_async("~/.lancedb")
@@ -472,6 +488,11 @@ async def connect_async(
     ...     db = await lancedb.connect_async("s3://my-bucket/lancedb",
     ...                                      storage_options={
     ...                                          "aws_access_key_id": "***"})
+    ...     # Azure credentials can also be passed directly
+    ...     db = await lancedb.connect_async(
+    ...         "az://my-container/my-database",
+    ...         storage_options=azure_storage_options,
+    ...     )
     ...     # For tests and temporary data, use an in-memory database
     ...     db = await lancedb.connect_async("memory://")
     ...     # Connect to LanceDB cloud