Add tests for chemistry children that require NMA_Chemistry_SampleInfo #474

Description:

We now have coverage for radionuclides requiring chemistry_sample_info_id, but we don’t have equivalent tests for other chemistry children. Add tests to ensure these models enforce the parent sample info requirement and
validate their relationships.

Scope / Targets:

• NMA_MajorChemistry
• NMA_MinorTraceChemistry
• NMA_FieldParameters

Notes:

• Confirm correct model names and relationships in db/nma_legacy.py.
• Avoid duplicating existing coverage; check tests/test_major_chemistry_legacy.py, tests/integration/test_nma_legacy_relationships.py, and any step files.

Acceptance Criteria:

• Each listed chemistry child has a test that:
  • fails when chemistry_sample_info_id is missing/null
  • verifies relationship navigation from NMA_Chemistry_SampleInfo (back_populates)
• Tests are placed in a clearly labeled section/class (e.g., TestChemistryChildrenRequireSampleInfo) or aligned with existing test organization.
• Integration/feature tests updated if they currently assume a thing_id FK for these children.

Proposed Tasks:

1. Add unit/integration tests for each child’s missing chemistry_sample_info_id (expect ValueError/IntegrityError as appropriate).
2. Add relationship navigation tests from NMA_Chemistry_SampleInfo to each child.
3. Run relevant test suites.