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/marketing/tarifs.html

@@ -36,7 +36,7 @@
       </h2>
     </div>
 
-    <div class="overflow-x-auto rounded-xl border border-brand-border">
+    <div class="overflow-x-auto rounded-lg border border-brand-border">
       <table class="w-full min-w-[720px] text-sm">
         <caption class="sr-only">Comparaison détaillée des 3 forfaits DictIA sur 8 caractéristiques</caption>
         <thead class="bg-brand-bg">
@@ -94,7 +94,7 @@
       <div x-data="{ open: false }" class="py-2">
         <h3>
           <button type="button"
-                  class="w-full flex items-center justify-between gap-4 py-4 text-left hover:bg-brand-navy/[0.03] transition-colors rounded-md px-2 focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2"
+                  class="w-full flex items-center justify-between gap-4 py-4 text-left hover:bg-brand-navy/[0.03] transition-colors rounded px-2 focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2"
                   @click="open = !open"
                   :aria-expanded="open.toString()"
                   aria-controls="tarifs-faq-panel-{{ loop.index }}">