fix: rename go module to allow go install to work

[JeremyLoy]

the error message is as follows:

$ GOBIN=bin go install github.com/openfga/model-visualizer/cmd@main        
go: github.com/openfga/model-visualizer/cmd@main: version constraints conflict:
        github.com/openfga/model-visualizer@v0.0.0-20250904214902-92619eb3d433: parsing go.mod:
        module declares its path as: weighted-graph-viz
                but was required as: github.com/openfga/model-visualizer

Description

What problem is being solved?

How is it being solved?

What changes are made to solve it?

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[curfew-marathon]

This PR has had no human activity for 90 days, so it has been marked lifecycle/stale.

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