Add settlements repository guardian

[EstandarMustaq]

Summary

• Add repository-local MAVULA Guardian checks.
• Add CODEOWNERS and pull request templates.
• Prepare the repository for required guardian status checks on main.

Validation

• Local guardian check passed.
• Relevant build, test, contracts and static validation were run from finance-platform.

Notes

• This change is part of the open-core repository protection rollout.