There is substantial duplicated DTO <-> domain mapping logic here (e.g., `macrosToDomain`/`macrosToDTO`, `itemToDomain`/`itemToDTO`) that now appears in multiple Supabase gateways/repositories. This increases the chance of subtle drift/bugs if one copy is updated and others aren’t. Consider extracting these into a shared helper that still preserves encapsulation (e.g., a `createSupabaseItemMapper()` / `createSupabaseMacroMapper()` factory module that is the only export).

[marcuscastelo]

There is substantial duplicated DTO <-> domain mapping logic here (e.g., macrosToDomain/macrosToDTO, itemToDomain/itemToDTO) that now appears in multiple Supabase gateways/repositories. This increases the chance of subtle drift/bugs if one copy is updated and others aren’t. Consider extracting these into a shared helper that still preserves encapsulation (e.g., a createSupabaseItemMapper() / createSupabaseMacroMapper() factory module that is the only export).

Originally posted by @Copilot in #1471 (comment)