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/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-[20px]{% endif %}">
+<div class="relative {% if recommended %}grad-bg p-[1.5px] rounded-xl{% 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-[18px] border border-brand-border h-full flex flex-col">
+  <div class="bg-white p-8 rounded-xl 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>