Phase 1 of structured quantities + UoM. Introduces a global UnitOfMeasure
catalog (Code-keyed for stable backend lookup of canonical units like
"each") and FamilyUnitOfMeasure for family-scoped customs, mirroring the
product-catalog pattern. Endpoints expose the merged effective catalog
plus CRUD for family customs. Abbreviation uniqueness is enforced per
table at the DB layer and across tables at the API layer.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Josh Rogers