Add implicit default origin in case of port 80

[m-breitbach]

Motivation and Context

In case of client port 80, origin http://localhost without explicit port should be accepted by default.

How Has This Been Tested?

Tested locally.

Breaking Changes

I would guess that nobody relies on that behavior.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation update

Checklist

• [x] I have read the MCP Documentation
• [x] My code follows the repository's style guidelines
• [x] New and existing tests pass locally
• [x] I have added appropriate error handling
• [x] I have added or updated documentation as needed

Additional context

None.