feat(auth-ui): complete Auth UI Kit (3.2) — 7 new components, 54 tests
New components:
- RegisterForm — name, email, password, confirm, terms, password strength
- ForgotPasswordForm — email input with success/error states, back link
- ResetPasswordForm — new password + confirm with strength indicator
- VerifyEmailForm — 6-digit code input with resend, numeric-only filter
- OnboardingShell — step indicator, progress bar, back/next/complete nav
- AuthPageLayout — full-page centered card with product branding
- PasswordStrengthBar — visual bar + label (weak/fair/good/strong)
Existing components preserved: LoginForm, MfaChallenge, SocialButtons
All styled via --bl-* CSS custom properties for product theming
54 tests (13 existing + 41 new) — all passing
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