#2 Title: test: write integration tests for multi-role verification using testutils

[N-thnI]

Description

To push our test coverage past our 95%+ target threshold, we need standalone integration tests simulating distinct ecosystem actors inside Valo-Core.

Todo

• Create isolated test mock environments for Sponsor, Maintainer, and Contributor addresses.
• Assert that unauthorized users attempting to invoke release_reward trigger an explicit contract failure.
• Validate correct state transitions across the lifecycle enum.