Onboarding flow is functional on mobile devices

More than half of web traffic is mobile. A signup or onboarding flow that overflows on a 375px screen doesn't just frustrate users — it locks out a majority of potential customers before they ever see the product. WCAG 2.2 SC 2.5.5 sets a 44px minimum touch target to prevent mis-taps; Section 508 §502.3.3 requires platform accessibility. A fixed-width onboarding form isn't a cosmetic issue: it's a conversion failure that compounds every day it ships.

In src/app/(auth)/layout.tsx, replace fixed-width containers with responsive fluid layouts:

<div className="flex min-h-screen items-center justify-center p-4">
  <Card className="w-full max-w-md">
    {children}
  </Card>
</div>

All buttons must use h-11 (44px) or taller. Audit every form input with className containing a fixed w-[N]px value and replace with w-full. Test at 375px viewport width — if anything scrolls horizontally, it fails.