feat(admin) : add client tickets tab with list, filters, status change, and delete

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/pages/admin.vue

@@ -27,6 +27,7 @@
             <AdminPriorityTab v-if="activeTab === 'priorities'" />
             <AdminTagTab v-if="activeTab === 'tags'" />
             <AdminUserTab v-if="activeTab === 'users'" />
+            <AdminClientTicketTab v-if="activeTab === 'client-tickets'" />
             <AdminGiteaTab v-if="activeTab === 'gitea'" />
             <AdminBookStackTab v-if="activeTab === 'bookstack'" />
         </div>
@@ -43,6 +44,7 @@ const tabs = [
     { key: 'priorities', label: 'Priorités' },
     { key: 'tags', label: 'Tags' },
     { key: 'users', label: 'Utilisateurs' },
+    { key: 'client-tickets', label: 'Tickets client' },
     { key: 'gitea', label: 'Gitea' },
     { key: 'bookstack', label: 'BookStack' },
 ] as const