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/pricing_card.html

@@ -15,9 +15,9 @@
    The button macro autoescapes its `text` arg, so `name` MUST NOT contain HTML entities
    (verified: "DictIA 8", "DictIA 16", "DictIA Cloud" are all entity-free). #}
 {%- macro pricing_card(slug, name, price_setup, price_monthly, target, features, recommended=False, cta_url='/checkout') -%}
-<div class="relative {% if recommended %}grad-bg p-[1.5px] rounded-xl{% endif %}">
+<div class="relative {% if recommended %}grad-bg p-[1.5px] rounded-lg{% endif %}">
   {% if recommended %}<span class="absolute -top-3 left-1/2 -translate-x-1/2 grad-bg text-white text-xs font-bold px-3 py-1 rounded-full shadow-cta">★ RECOMMANDÉ</span>{% endif %}
-  <div class="bg-white p-8 rounded-xl border border-brand-border h-full flex flex-col">
+  <div class="bg-white p-8 rounded-lg border border-brand-border h-full flex flex-col">
     <div class="mb-6">
       <h3 class="text-xl font-black mb-1 text-brand-navy">{{ name | safe }}</h3>
       <p class="text-sm text-brand-navy/70">{{ target | safe }}</p>