feat: bouton renvoyer le code sur page verification echeancier

- Route /echeancier/verify/{id}/resend (POST)
- Genere nouveau code 6 chiffres + envoie par email
- Bouton "Renvoyer le code" sous le formulaire

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/echeancier/verify.html.twig

@@ -28,6 +28,10 @@
             </form>
 
             <p class="text-center text-xs text-gray-400 mt-4">Le code expire dans 15 minutes.</p>
+
+            <form method="post" action="{{ path('app_echeancier_resend_code', {id: echeancier.id}) }}" class="mt-3 text-center">
+                <button type="submit" class="text-xs font-bold uppercase tracking-wider text-gray-500 hover:text-gray-900 underline transition-all">Renvoyer le code</button>
+            </form>
         </div>
     </div>
 </div>