The foreign key sql_workbench_result_snapshot.notebook_id had no index.
NotebookService lists a notebook's snapshots by it, the notebook delete
cascade and the child record lock use it, and the notebook page's Runs
list joins executions on notebook_id. The reference DDL and the H2 test
schema add both indexes. The Postgres integration test now fails if any
sql_workbench_ foreign-key column lacks a leading index.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>