Adds a `refresh_tokens` table (migration 003) with one row per live
refresh token, keyed by UUID jti. On every POST /api/auth/refresh the
old jti row is deleted and a new token pair is issued and stored. Using
a consumed token returns 401. Expired rows are pruned inline on each
successful rotation.
Server: Claims gains an optional `jti` field; make_refresh_token now
returns (jwt, jti); register/login insert the jti row; RefreshResponse
now carries both tokens. Client: stores the rotated refresh token from
the response. ARCHITECTURE.md: API table + Security Model updated.
Three new integration tests cover rotation, consumed-token rejection,
and chained rotations.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
funman300