test: cover endpoint, protocol, port, and TLS matrix - #10

Summary

• Add regression coverage for HTTP and HTTPS endpoints.
• Cover custom HTTP/HTTPS ports and endpoint normalization.
• Cover TLS certificate verification enabled/disabled.
• Verify boto3 client configuration follows the canonical configuration layer.
• Ensure endpoint protocol and boto3 settings cannot silently disagree.

Acceptance criteria

• HTTP/HTTPS behavior has a single, documented source of truth.
• Endpoint URLs and boto3 client configuration cannot silently disagree.
• Custom ports continue to work correctly.
• TLS verification behavior is explicit and tested.
• Existing valid configurations remain compatible where practical.
• Tests cover endpoint, protocol, port, and TLS combinations.

This PR is a follow-up because the original SSL/endpoint PR was accidentally merged and closed.