refactor(ui): modernize button + input border radii (rounded-lg/md/xl, sharper SaaS aesthetic)

Aligns DictIA marketing/auth/legal/billing templates with modern SaaS visual
conventions (Linear, Vercel, Stripe Dashboard, Notion). Old radii (12-18px)
felt dated; new system uses 6-12px for tighter, more contemporary corners.

Border radius system:
- Buttons (CTA, submit, secondary): rounded-[0.75rem] (12px) -> rounded-lg (8px)
- Form inputs (text/email/password/select/textarea/checkbox): rounded-[0.5rem] -> rounded-md (6px)
- Cards (pricing, bento, modals, content panels): rounded-[18px]/[14px]/[12px] -> rounded-xl (12px)
- Pricing card outer gradient frame: rounded-[20px] -> rounded-xl (matches inner)
- Pills / badges / status chips: KEEP rounded-full
- Avatars / circular icon containers: KEEP rounded-full
- Code blocks: KEEP rounded (4px)

Decision tree applied for ambiguous cases:
- Button-like clickable CTA -> rounded-lg
- Form input -> rounded-md
- Card / panel / modal -> rounded-xl
- Badge / pill / chip / avatar -> rounded-full (preserved)

In-scope templates modified (23):
- macros/button.html (central macro, cascades to all callers)
- macros/pricing_card.html, macros/bento.html
- marketing/landing.html, tarifs.html, fonctionnalites.html, conformite.html, contact.html
- auth/check_email.html, forgot_password.html, magic_link_request.html, oauth_finish_signup.html,
  passkey_setup.html, reset_password.html, totp_setup.html, totp_verify.html, verify_success.html
- billing/cancel.html, billing/success.html
- legal/_layout.html, legal/index.html
- register.html, login.html

Out of scope (untouched): index.html, account.html, admin.html, share.html, inquire.html,
group-admin.html, components/**, includes/**, modals/** (all legacy Speakr Vue surfaces).

Tests: test_marketing_landing_template.py — 2 assertions updated to match new bento icon
(rounded-md) and pricing card frame (rounded-xl). All 18 legal tests + 58 marketing landing
tests + 9 signup_loi25 tests still pass. Decorative rounded-full preserved on hero cosmic
orbs and ordres-pros avatar circles.

Diff: 94 insertions / 94 deletions (1:1 mechanical replacement, no class drift).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

templates/legal/_layout.html

@@ -221,7 +221,7 @@
     <article id="main-content"
              role="main"
              aria-labelledby="legal-title"
-             class="bg-white p-6 md:p-10 rounded-[18px] border border-brand-border shadow-cta order-1">
+             class="bg-white p-6 md:p-10 rounded-xl border border-brand-border shadow-cta order-1">
       <header class="mb-8 pb-6 border-b border-brand-border">
         <p class="text-xs uppercase tracking-wider text-brand-navy/70 mb-2">Document légal DictIA</p>
         <h1 id="legal-title" class="text-3xl md:text-4xl font-black text-brand-navy mb-4 tracking-tight">{{ title }}</h1>
@@ -244,8 +244,8 @@
       </header>
 
       {# TOC mobile (collapsible) — visible < lg seulement #}
-      <details class="lg:hidden mb-6 border border-brand-border rounded-[12px] bg-brand-bg/50">
-        <summary class="cursor-pointer px-4 py-3 text-sm font-semibold text-brand-navy flex items-center justify-between focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 rounded-[12px]">
+      <details class="lg:hidden mb-6 border border-brand-border rounded-xl bg-brand-bg/50">
+        <summary class="cursor-pointer px-4 py-3 text-sm font-semibold text-brand-navy flex items-center justify-between focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 rounded-xl">
           <span>Sur cette page</span>
           <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"
                stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
@@ -268,7 +268,7 @@
         {% if prev_page %}
         <a href="{{ url_for('legal.legal_page', page=prev_page) }}"
            rel="prev"
-           class="block p-4 bg-brand-bg/60 border border-brand-border rounded-[12px] hover:border-brand-b1 hover:bg-white transition focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2">
+           class="block p-4 bg-brand-bg/60 border border-brand-border rounded-xl hover:border-brand-b1 hover:bg-white transition focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2">
           <span class="block text-xs uppercase tracking-wider text-brand-navy/60 mb-1">
             <span aria-hidden="true">←</span> Précédent
           </span>
@@ -281,7 +281,7 @@
         {% if next_page %}
         <a href="{{ url_for('legal.legal_page', page=next_page) }}"
            rel="next"
-           class="block p-4 bg-brand-bg/60 border border-brand-border rounded-[12px] hover:border-brand-b1 hover:bg-white transition focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 sm:text-right">
+           class="block p-4 bg-brand-bg/60 border border-brand-border rounded-xl hover:border-brand-b1 hover:bg-white transition focus-visible:outline-2 focus-visible:outline-brand-b1 focus-visible:outline-offset-2 sm:text-right">
           <span class="block text-xs uppercase tracking-wider text-brand-navy/60 mb-1">
             Suivant <span aria-hidden="true">→</span>
           </span>
@@ -304,7 +304,7 @@
            aria-label="Table des matières">
       <div x-data="legalToc()"
            x-init="init()"
-           class="legal-toc bg-white border border-brand-border rounded-[14px] p-5 mt-0">
+           class="legal-toc bg-white border border-brand-border rounded-xl p-5 mt-0">
         <h2 class="text-xs font-bold uppercase tracking-wider text-brand-navy/70 mb-3">
           Sur cette page
         </h2>