The cascade-delete commit (5a5a8b6) added blockRepository.deleteByAnnotationId()
to AnnotationService.deleteAnnotation(), but the test class was not updated to
mock TranscriptionBlockRepository. Mockito injected null, causing deleteAnnotation_succeeds_whenOwner
to throw NPE. Adds the mock, verifies the cascade call, and adds an inOrder test
asserting the block is deleted before the annotation.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>