pre-commit runs `tofu validate`/tflint on modules/artifactapi standalone, where
no required_providers was declared, so OpenTofu inferred hashicorp/artifactapi
and failed (and tflint flagged missing required_version/version constraint).
- add modules/artifactapi/versions.tf declaring required_version and the
artifactapi provider (source = the registry, version >= 0.1.2)
- drop the now-duplicate required_providers from root.hcl's generated backend.tf;
keep the provider config block + backend. Declaring it in both the module and
the generated root would be a "Duplicate required providers" error at runtime.
Also revert the earlier init lock-cleanup: the CI failure was stale provider
references in state (fixed with `tofu state replace-provider`), not the lock.
