refactor(ui): sharpen buttons + inputs to rounded (4px) for modern minimal SaaS look

V2 sharper radii system aligned with Stripe Dashboard / Linear / Vercel
aesthetic — the v1 rounded-lg (8px) on buttons still felt too soft.

New scale:
- Buttons (CTA, submit, ghost, secondary): rounded-lg → rounded (4px)
- Form inputs (text/email/password/select/textarea): rounded-md → rounded (4px)
- Checkboxes: rounded-sm (2px) added explicitly to consent + remember-me
- Cards (pricing, bento, content panels): rounded-xl → rounded-lg (8px)
- Small icon tiles (w-10 h-10 / w-12 h-12 grad-bg squares): rounded-md → rounded
- Pills, badges, avatars, status orbs: rounded-full (KEPT)
- Inline code in legal CSS: rounded (4px) (KEPT)
- Legal blockquote/pre/draft-callout border-radius: 8px → 4px

Files modified (24):
- templates/macros/{button,bento,pricing_card}.html
- templates/marketing/{landing,tarifs,fonctionnalites,conformite,contact}.html
- templates/auth/{check_email,forgot_password,magic_link_request,
  oauth_finish_signup,passkey_setup,reset_password,totp_setup,totp_verify,
  verify_success}.html
- templates/billing/{success,cancel}.html
- templates/legal/{_layout,index}.html
- templates/{register,login}.html
- tests/test_marketing_landing_template.py (assertions updated to match v2)

Verification:
- 18/18 legal page tests pass (tests/_run_legal_pages_windows.py)
- 58/58 marketing landing tests pass

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

templates/legal/index.html

@@ -33,7 +33,7 @@
 
 {% block content %}
 <a href="#main-content"
-   class="sr-only focus:not-sr-only focus:fixed focus:top-2 focus:left-2 focus:z-[100] focus:px-4 focus:py-2 focus:bg-brand-navy focus:text-white focus:rounded-lg focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2">
+   class="sr-only focus:not-sr-only focus:fixed focus:top-2 focus:left-2 focus:z-[100] focus:px-4 focus:py-2 focus:bg-brand-navy focus:text-white focus:rounded focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2">
   Aller au contenu principal
 </a>
 
@@ -68,13 +68,13 @@
           <a href="{{ page.url }}"
              target="_blank"
              rel="noopener noreferrer"
-             class="legal-card is-external group block h-full p-5 md:p-6 bg-white border border-brand-border rounded-xl hover:border-brand-b1 hover:shadow-cta focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 relative">
+             class="legal-card is-external group block h-full p-5 md:p-6 bg-white border border-brand-border rounded-lg hover:border-brand-b1 hover:shadow-cta focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 relative">
         {% else %}
           <a href="{{ url_for('legal.legal_page', page=page.slug) }}"
-             class="legal-card group block h-full p-5 md:p-6 bg-white border border-brand-border rounded-xl hover:border-brand-b1 hover:shadow-cta focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 relative">
+             class="legal-card group block h-full p-5 md:p-6 bg-white border border-brand-border rounded-lg hover:border-brand-b1 hover:shadow-cta focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 relative">
         {% endif %}
           <div class="flex items-start gap-4">
-            <div class="legal-card-icon shrink-0 inline-flex items-center justify-center w-12 h-12 rounded-xl">
+            <div class="legal-card-icon shrink-0 inline-flex items-center justify-center w-12 h-12 rounded">
               {{ page.icon | safe }}
             </div>
             <div class="flex-1 min-w-0">
@@ -97,7 +97,7 @@
     </ul>
 
     {# Bloc info pied — signature, contact, sous-processeurs #}
-    <aside class="mt-12 max-w-3xl mx-auto bg-white border border-brand-border rounded-xl p-6 md:p-7"
+    <aside class="mt-12 max-w-3xl mx-auto bg-white border border-brand-border rounded-lg p-6 md:p-7"
            aria-label="Informations complémentaires sur les documents légaux">
       <p class="text-sm text-brand-navy/80 leading-relaxed mb-3">
         Documents signés numériquement par <strong class="text-brand-navy">Allison Rioux</strong>,