fix(marketing): WCAG 2.3.3 reduced-motion + defensible social proof + em-spacing

- Add @media (prefers-reduced-motion: reduce) override to disable animations
  for vestibular-sensitive users (covers hero + future scroll/infinite anims)
- Replace 5-star icon + '27 cabinets' claim with shield + 'Conçu avec 9
  ordres professionnels' + 'Pré-inscription ouverte' (LPC art. 219 +
  Competition Act s. 52 compliance — pre-launch claims must be factual)
- Convert H1/H2/H3 letter-spacing from absolute px to em-relative (-3px →
  -0.028em on H1) so tracking scales correctly with clamp font-size on mobile
- Update test_hero_has_social_proof_microcopy to assert new copy

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

templates/marketing/landing.html

@@ -1,7 +1,7 @@
 {% extends 'marketing/base.html' %}
 
 {% block title %}Transcription IA conforme Loi 25 — DictIA pour avocats, CPA, secteur public{% endblock %}
-{% block description %}DictIA transcrit vos réunions confidentielles 100% au Québec. Conforme Loi 25, Barreau, CPA, ChAD. Lancement printemps 2026 — 27 cabinets pilotes.{% endblock %}
+{% block description %}DictIA transcrit vos réunions confidentielles 100% au Québec. Conforme Loi 25, Barreau, CPA, ChAD. Conçu avec 9 ordres professionnels — lancement printemps 2026.{% endblock %}
 
 {% block content %}
 {# ===== HERO ===== #}
@@ -50,10 +50,16 @@
         {{ button('Voir les tarifs →', href='/tarifs', variant='ghost', size='lg') }}
       </div>
 
-      {# Social proof microcopy — above-the-fold trust signal #}
+      {# Social proof microcopy — defensible: refers to pre-launch waitlist + factual ordres pros count #}
       <p class="mt-8 text-sm text-white/50 animate-tc-fade-in-up" style="animation-delay: 400ms; animation-fill-mode: backwards;">
-        <span class="text-yellow-400" aria-hidden="true">★★★★★</span>
-        <span class="ml-2">27 cabinets québécois nous font confiance</span>
+        <span class="inline-flex items-center gap-1.5">
+          <svg width="14" height="14" viewBox="0 0 20 20" fill="currentColor" class="text-brand-b3" aria-hidden="true">
+            <path d="M10 2L3 5v5.5c0 4.04 2.84 7.85 7 8.5 4.16-.65 7-4.46 7-8.5V5l-7-3z"/>
+          </svg>
+          <span>Conçu avec 9 ordres professionnels québécois</span>
+        </span>
+        <span class="mx-2 text-white/30">·</span>
+        <span>Pré-inscription ouverte</span>
         <span class="mx-2 text-white/30">·</span>
         <span>Lancement printemps 2026</span>
       </p>