Migrate to oa-configurator 1.0

[nicoloesch]

Depends on: oa-configurator. , must merge and publish first. This PR bumps pyproject.toml's oa-configurator pin from ==0.1.2 to whatever the published 1.0 version is (currently a # TODO marker in the diff, deliberately left unbumped pending publish).

Summary

• Migrate OrmLoaderConfig off the removed ResourceRef/ResourceSpec/test_resources shape: no PackageConfigBase.get_engine() scaffolding needed since orm-loader owns no production database resources.
• Adds orm-loader's first-ever RefTo field: test_orm_db: Annotated[str | None, RefTo(DatabaseConfig, is_test=True)] = None. Replaces the old TEST_DB ClassVar, which named a test database with nothing backing it.
• tests/conftest.py: resolve_test_resource(OrmLoaderConfig.TEST_DB) → resolve_test_database(OrmLoaderConfig, "test_orm_db") (explicit field name, no auto-discovery).
• tests/loaders/test_pg_loader.py: @pytest.mark.requires_resource(OrmLoaderConfig.TEST_DB) → @pytest.mark.requires_database("test_orm_db") (17 call sites).
  • requires_database takes a plain string; pytest markers are collection-time-evaluated, so a field reference isn't possible there.
  • A stale/renamed string fails loudly via resolve_database, not silently. See oa-configurator's own PR, "Test-database wiring," for the full reasoning.
• pyproject.toml: added # TODO: bump to >=1.0.0,<2.0.0 once oa-configurator 1.0 is published markers on both the main and dev oa-configurator pins.

Relationship to open PRs and issues

• Absorbs Widen oa-configurator pin to a semver range #25 's range-widening intent, which becomes stale.
• Closes Relax oa-configurator pin to a semver range #24