feat(mail) : intègre onglet Mail dans pages/admin.vue

frontend/pages/admin.vue

@@ -30,6 +30,7 @@
             <AdminGiteaTab v-if="activeTab === 'gitea'" />
             <AdminBookStackTab v-if="activeTab === 'bookstack'" />
             <AdminZimbraTab v-if="activeTab === 'zimbra'" />
+            <AdminMailTab v-if="activeTab === 'mail'" />
         </div>
     </div>
 </template>
@@ -48,6 +49,7 @@ const tabs = [
     { key: 'gitea', label: 'Gitea' },
     { key: 'bookstack', label: 'BookStack' },
     { key: 'zimbra', label: 'Zimbra' },
+    { key: 'mail', label: 'Mail' },
 ] as const
 
 type TabKey = typeof tabs[number]['key']