Additive-only: pages still use lib/api/* and constants/queryKeys.ts until
the page-migration agents run. Each domain ships api.ts (HTTP moved from
lib/api), types.ts (contract re-exports + view types), schemas.ts (contract
schema re-exports + form schemas with toRequest mappers), and use-cases.ts
(TanStack Query v5 hooks + hierarchical query keys, mirroring current page
invalidations and toast-on-error behavior).
Adds an explicit vite/vitest alias for the
@proposal-system/api-contracts/schemas subpath (package has no exports map)
plus a schema/mapper smoke test suite.
