feat: add artifactapi_local_terraform resource type

New resource for creating local terraform registries in ArtifactAPI
(repo_type=local, package_type=terraform). These repos host providers
directly rather than proxying an upstream registry.

Schema is minimal: just name and description — no upstream-specific
fields like base_url, caching TTLs, or auth.

internal/provider/provider.go

@@ -68,6 +68,7 @@ func (p *ArtifactAPIProvider) Resources(_ context.Context) []func() resource.Res
 		newRemoteResource("terraform"),
 		newRemoteResource("goproxy"),
 		NewVirtualResource,
+		NewLocalTerraformResource,
 	}
 }