Expose compatible model versions in release manifest backfill

[MaxGhenis]

Summary

• add a backfill CLI/workflow option for additional compatible policyengine-us runtime versions
• keep the build model version separate from additional compatibility certs
• bump policyengine-us to 1.722.4 so the freshness guard remains current
• cover the new behavior in the backfill unit tests

Verification

• env -u UV_FROZEN uv run python -m pytest tests/unit/test_backfill_release_manifest.py -q
• env -u UV_FROZEN uv run python -m ruff check policyengine_us_data/storage/backfill_release_manifest.py tests/unit/test_backfill_release_manifest.py
• env -u UV_FROZEN uv run python -m ruff format --check policyengine_us_data/storage/backfill_release_manifest.py tests/unit/test_backfill_release_manifest.py
• env -u UV_FROZEN uv run python .github/scripts/check_policyengine_us_dependency.py