Implement staging table changes of orm-loader

[nicoloesch]

Summary

• Fixes Replace staging-schema/search_path fallthrough with native orm_loader schema support #17

• cli_vocab.py: staging schema isolation is now driven by orm-loader's backend rather than a search_path workaround (see Overhauled staging tables with schemas and centralised specifiers orm-loader#22)

  • ensure_schema is called for STAGING_SCHEMA
  • the connect listener sets search_path to db_schema only (staging schema no longer needs to be on the path because orm-loader qualifies staging identifiers explicitly).

• Guard added: raises ValueError if db_schema == STAGING_SCHEMA to prevent silent schema collision.

• _is_missing_staging_table_error now derives the staging table name via resolve_backend(session).staging_name_for_table(model.__tablename__) instead of calling the removed model.staging_tablename() protocol method.

TODO

Depends on AustralianCancerDataNetwork/orm-loader#22 to pass. Requires:

• orm-loader version bump. This will also make the CI pass as it will get the newest changes in.