Add PK to history tables in the DB

**User Story**
As an EDW user, I would like to have primary keys in the history tables to simplify ETL processing and make API pagination more reliable. Not urgent now, but would be important on larger data volumes.

**Acceptance Criteria**
- [ ] Add PK to history tables in DB

Start by locating the database schema and definitions for the history tables mentioned in the issue, then review how ETL processing and API pagination use them. Done means primary keys are added to the history tables, but the issue names no files, migrations, or tests to guide validation.

Written by the indexing model from the issue text.