Sync release manifest bundle versions

[anth-volk]

Fixes #336

Summary

• Sync bundled release manifest bundle_id and policyengine_version fields during release version bumps.
• Add a provenance helper so manual country bundle refreshes also preserve the current policyengine.py bundle identity.
• Update the checked-in US and UK manifest identities from 4.0.0 to 4.3.1.
• Add tests for the bump script, bundle refresh path, and bundled release manifest identity.

Testing

• uv run ruff check .github/bump_version.py src/policyengine/provenance/bundle.py src/policyengine/provenance/__init__.py tests/test_bump_version.py tests/test_bundle_refresh.py tests/test_release_manifests.py
• uv run pytest tests/test_bump_version.py tests/test_bundle_refresh.py tests/test_release_manifests.py -q