IProductService/ProductService return display-ready DTOs (BrandName/
ConceptName resolved via join) rather than raw Product entities.
ProductController routes match AGENTS.md §11; price/insight fields
deferred until CW-EPIC-05 exists.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Brand, Product (aggregate root for ProductIdentifier), ProductIdentifier,
and HouseholdProductPreference, per AGENTS.md §5.2/5.3. Built ahead of
MVP-tagged epics per DEC-010 (explicit founder direction to work epics
in strict numeric order).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Add toggle/skip/delete with optimistic concurrency handling and jQuery
progressive enhancement (CW-STORY-03.4), then a mobile-first touch-target
and quick-add polish pass (CW-STORY-03.5).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>