Use ExpectedBucketOwner param in S3 calls

SonarCloud flagged the following lines:

```python
try:
uploads_response = S3_CLIENT.list_multipart_uploads(Bucket=bucket_name)
```
and

```python
try:
file_parts_response = S3_CLIENT.list_parts(
```

For both of these, the message is: "Add the 'ExpectedBucketOwner' parameter to verify S3 bucket ownership."

Search the Python codebase for the list_multipart_uploads and list_parts S3 calls shown in the issue. Start by reading their surrounding upload logic, then ensure both calls verify bucket ownership with the requested parameter and run the relevant existing tests if available.

Written by the indexing model from the issue text.