objects/s3: add force_path_style option and use path-style addressing when set (MinIO compatibility)

[chunghoduc]

Summary:
Add a force_path_style option to the S3 provider and use it to switch the AWS SDK to path-style bucket addressing. This enables compatibility with MinIO and other S3-compatible endpoints that don’t support virtual-hosted-style URLs.

Changes:

Proto: add BucketCluster.S3.force_path_style.
Infra mapping: accept force_path_style in JSON and pass it to runtime.
S3 client: enable AWS SDK path-style when force_path_style is true.
Why:

MinIO and some custom/local endpoints require path-style (https://endpoint/bucket/key) instead of virtual-hosted-style.
Usage:

Set force_path_style: true in your S3 provider config.
Example:
"force_path_style": true
Backwards compatibility:

Default is false; behavior unchanged unless enabled.

[encore-cla]

All committers have signed the CLA.