Splits the 2571-line cassandra.css into ten focused stylesheets:
tokens (palette + fonts), layout (chrome), panels, dashboard,
portfolio, log-chat, auth, settings, news, public. base.html and
public_base.html load only what they need; auth pages (login,
verify, unsubscribe confirm) load tokens + layout + auth.
Brand drift-detection test repointed at tokens.css (where the
palette now lives). 291 tests still pass.
