refactor(ui): V3 fully square buttons + inputs (rounded-none, brutalist/Swiss aesthetic)

V3 finalizes the radii pass to a fully brutalist/Swiss visual language:

- Buttons (CTAs, submit, secondary, ghost, OAuth provider tiles): rounded-none (0px)
- Form inputs (text/email/password/select/textarea/code-entry): rounded-none (0px)
- Checkboxes: rounded-none (0px) — was rounded-sm
- Small icon tiles (w-10 h-10 / w-12 h-12 grad-bg squares): rounded-none (0px)
- Inline code blocks (totp recovery <pre>, secret <code>): rounded-none (0px)
- Cards (pricing, bento, content panels, modals, prev/next nav): rounded (4px) — was rounded-lg
- Alert / flash boxes: rounded (4px) — was rounded-lg
- Pills, badges, status chips, ordres pros avatars, decorative cosmic orbs: rounded-full preserved
- Legal _layout.html inline <style> blockquote/pre/code/draft-callout: border-radius 0 — was 4px

Updated tests/test_marketing_landing_template.py assertions:
- bento icon assertion: "grad-bg rounded " -> "grad-bg rounded-none "
- pricing recommended frame: "rounded-lg" -> "rounded" (with strict trailing-char match to avoid rounded-none false positive)

Verification: 18/18 legal tests pass, 58/58 marketing landing tests pass, 5/5 root redirect tests pass. Two pre-existing failures in test_marketing_secondary_pages (SOC 2 hedge text + gitea.innova-ai.ca URL) are unrelated to this radii pass.

templates/billing/success.html

@@ -27,7 +27,7 @@
     </h2>
 
     <ol class="space-y-6">
-      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">1</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Confirmation par courriel</h3>
@@ -37,7 +37,7 @@
         </div>
       </li>
 
-      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">2</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Activation de votre abonnement</h3>
@@ -47,7 +47,7 @@
         </div>
       </li>
 
-      <li class="bg-white p-6 rounded-lg border border-brand-border flex gap-4">
+      <li class="bg-white p-6 rounded border border-brand-border flex gap-4">
         <span class="grad-bg text-white font-black w-10 h-10 rounded-full flex items-center justify-center flex-shrink-0 shadow-cta" aria-hidden="true">3</span>
         <div>
           <h3 class="font-bold text-brand-navy mb-1">Mise en service</h3>