test(legacy): add zero address validation for setOwner

[forumevi]

This test ensures that ownership cannot be accidentally transferred to address(0), which would permanently lock the proxy contract.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[forumevi]

@maintainers Hi! 👋

I've added a security test to ensure setOwner cannot be called with address(0), which would permanently lock the proxy contract.

The workflow is awaiting approval. Could someone please approve and run the CI checks?

Thanks! 🚀