Redesign the setup flow and consolidate the CSS into one primitives layer

Onboarding asks explicitly for one or two parents and shows one card per
parent for balances; the balance form is per parent with inline
validation; the partner can be filled from the FK deduction or added
from it. Settings and Dashboard reuse the same form.

CSS: bare buttons carry no colour any more; buttons, cards, choice
cards, fields, alerts, badges, eyebrow and modal chrome are defined once
in primitives.css. Media queries live only in responsive.css. A style
guard test blocks hex, !important and stray media queries. Bilingual
fixes: calendar selects size by content, header no longer wraps. Vitest
is capped at four workers.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/src/components/layout/Footer.tsx

@@ -7,7 +7,9 @@ export function Footer(): ReactNode {
   const currentYear = new Date().getFullYear()
   return (
     <footer role="contentinfo" data-testid="footer">
-      <p data-testid="footer-text">{t('footer.copyright', { year: currentYear })}</p>
+      <div className="footer__inner">
+        <p data-testid="footer-text">{t('footer.copyright', { year: currentYear })}</p>
+      </div>
     </footer>
   )
 }