chore(deps): update Go dependencies

[dcmcand]

Summary

• Update Go module dependencies with go get -u ./... and go mod tidy.
• Raise the module Go directive to 1.26.0, which is required by the latest Helm and Kubernetes dependency set.
• Remove obsolete staticcheck suppressions around Kubernetes fake clients after the dependency update.

Verification

• go test ./...
• make build
• Commit hooks: go fmt, go vet, golangci-lint, go test
• trivy fs --scanners vuln,misconfig --skip-dirs .git --skip-dirs .claude --skip-dirs .worktrees --skip-files .env .

Notes

• Trivy reports 0 vulnerabilities for go.mod after the update.
• Remaining Trivy findings are pre-existing Kubernetes security-context findings in pkg/argocd/templates/manifests/nebari-operator/deployment-patch.yaml.
• Release notes and changelogs were reviewed for the updated direct dependency families; no applicable breaking changes were found for current repository usage.