fix(versioning): retention task FK violation on cross-entity transactions

When one ORM flush touches multiple versioned entities (dashboard +
slice + dataset all save at tx=X), each gets a shadow row sharing
that tx. If only the dashboard is later edited at tx=Y, the
dashboard row at tx=X is closed (end_tx=Y) while slice/dataset rows
stay live at tx=X. Retention then preserves tx=X (slice/dataset are
live there) and prunes tx=Y. The dashboard's closed row at tx=X
survives step 1, then its end_transaction_id=Y trips the FK when
step 2 deletes version_transaction row Y.

Fix: extend the shadow-row delete to also match end_transaction_id
IN tx_ids. Live rows have end_tx=NULL so they're never matched by
either predicate. Closed rows that touch a pruned tx at either
endpoint are pruned together — consistent with retention semantics
(any tx in the row's lifespan is gone, so the row's chain is broken
anyway).

Unblocks test_retention_prunes_old_rows on sqlite, mysql, postgres.