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/macros/bento.html

@@ -3,10 +3,10 @@
    so dynamic `col-span-{{ span }}` would produce dead classes — the lookup keeps the utilities discoverable). #}
 {% macro bento_card(number, title, description, icon='✦', span='1') %}
 {%- set span_classes = {'1': 'col-span-1', '2': 'sm:col-span-2', '3': 'sm:col-span-2 md:col-span-3'} -%}
-<div class="relative bg-brand-navy2 p-6 rounded-xl overflow-hidden border border-white/[0.045] {{ span_classes.get(span, 'col-span-1') }}">
+<div class="relative bg-brand-navy2 p-6 rounded-lg overflow-hidden border border-white/[0.045] {{ span_classes.get(span, 'col-span-1') }}">
   <div class="absolute top-2 right-4 text-[80px] font-black text-white/[0.04]" aria-hidden="true">{{ number }}</div>
   <div class="relative">
-    <div class="w-10 h-10 grad-bg rounded-md mb-4 flex items-center justify-center text-lg">{{ icon }}</div>
+    <div class="w-10 h-10 grad-bg rounded mb-4 flex items-center justify-center text-lg">{{ icon }}</div>
     <h3 class="text-lg font-bold mb-2 text-white">{{ title | safe }}</h3>
     <p class="text-sm text-white/70">{{ description | safe }}</p>
   </div>