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/button.html

@@ -14,13 +14,13 @@
 {%- set sizing = sizes.get(size, sizes['md']) -%}
 {%- if as_button -%}
 <button type="{{ type }}"
-        class="inline-flex items-center justify-center gap-2 rounded-lg font-semibold transition-all duration-200 {{ classes }} {{ sizing }}">
+        class="inline-flex items-center justify-center gap-2 rounded font-semibold transition-all duration-200 {{ classes }} {{ sizing }}">
   <span>{{ text }}</span>
   {%- if icon -%}<span class="ml-0.5" aria-hidden="true">{{ icon | safe }}</span>{%- endif -%}
 </button>
 {%- else -%}
 <a href="{{ href }}"
-   class="inline-flex items-center justify-center gap-2 rounded-lg font-semibold transition-all duration-200 {{ classes }} {{ sizing }}"
+   class="inline-flex items-center justify-center gap-2 rounded font-semibold transition-all duration-200 {{ classes }} {{ sizing }}"
    {% if target %}target="{{ target }}"{% endif %}
    {% if rel %}rel="{{ rel }}"{% endif %}>
   <span>{{ text }}</span>