Restore Zenodo release archiving and standardize citation metadata

[bernalde]

Context

This is a package-level follow-up to JuliaQUBO/QUBO.jl#66.

• Current GitHub release: v0.6.5
• Existing Zenodo concept DOI: 10.5281/zenodo.7811951
• Latest archived version found during the 2026-07-27 audit:
  v0.3.3, DOI 10.5281/zenodo.13840948
• The repository has no CITATION.cff.

The existing concept DOI should be preserved. The gap is deposit management,
release archiving, and consistent citation metadata—not the absence of a DOI.

Scope

• Confirm who can currently manage the Zenodo deposit.
• Add at least two active JuliaQUBO maintainers with Can manage access,
  using a Zenodo support transfer if the existing owner cannot respond.
• Verify or restore GitHub release archiving.
• Archive the current supported release under the existing concept DOI.
• Decide whether any skipped historical version is needed for an existing
  citation; do not backfill every release by default.
• Add a valid CITATION.cff describing the current package and using the
  concept DOI as its evergreen software DOI.
• Keep the QUBO.jl journal article as the preferred ecosystem citation,
  while documenting that an exact QUBODrivers release should use its
  version DOI.
• Update the README DOI badge/link so it does not pin users to the
  historical v0.3.3 version DOI.
• Add Zenodo/citation verification to the release checklist or automated
  release checks.

Acceptance criteria

• The concept DOI remains 10.5281/zenodo.7811951.
• At least two active maintainers can manage the deposit.
• The current supported release has a Zenodo version record.
• README and CITATION.cff use concept-versus-version DOI semantics
  consistently.
• CITATION.cff validates against the supported CFF schema.
• The release process has a repeatable check for archival drift.

Do not mint a replacement concept DOI unless Zenodo confirms that transfer or
shared management of the existing record is impossible.