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/cancel.html

@@ -24,7 +24,7 @@
   <div class="max-w-[820px] mx-auto px-6">
     <h2 id="info-title" class="sr-only">Que faire ensuite</h2>
 
-    <div class="bg-white p-8 rounded-lg border border-brand-border mb-8">
+    <div class="bg-white p-8 rounded border border-brand-border mb-8">
       <h3 class="text-lg font-bold mb-3 text-brand-navy">Pourquoi avoir hésité&nbsp;?</h3>
       <p class="text-sm text-brand-navy/80 leading-relaxed mb-4">
         Si vous avez une question sur les forfaits, la conformité Loi&nbsp;25 ou la mise en service, notre équipe peut vous accompagner sans pression commerciale.