Cuts the 0.8.1 release. Picks up:
- All shadcn (new-york) migration work that landed after v0.8.0
  (16 primitives, login-04/signup-04 blocks, dark-mode + tokens).
- Frontend deps pinning fix (5404cf5) that unblocks pnpm dev on
  projects scaffolded by arqel:install.
- Documentation i18n (en + pt-BR + es) and sundry doc fixes.

CHANGELOG [Unreleased] section moved to [0.8.1] - 2026-05-05.

Signed-off-by: Diogo C. Coutinho <diogo.coutinho.ads@gmail.com>