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/billing/success.html

@@ -27,7 +27,7 @@
     </h2>
 
     <ol class="space-y-6">
-      <li class="bg-white p-6 rounded-xl border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">1</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Confirmation par courriel</h3>
@@ -37,7 +37,7 @@
         </div>
       </li>
 
-      <li class="bg-white p-6 rounded-xl border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">2</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Activation de votre abonnement</h3>
@@ -47,7 +47,7 @@
         </div>
       </li>
 
-      <li class="bg-white p-6 rounded-xl border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">3</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Mise en service</h3>