fix(measure): hide per-task "Visualizza Task" link for non-Maker operators

On the task list, each task card exposed a "Visualizza Task" link that jumps
straight into an individual task. Pure operators (MeasurementTec without
Maker) should follow the guided flow and start only with AVVIA. Gate the
per-task link behind the Maker role; admins/makers who also measure keep it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/frontend/flask_app/templates/measure/task_list.html

@@ -187,7 +187,8 @@
             </div>
           </div>
 
-          <!-- Action Button -->
+          <!-- Action Button (Maker only — operators start the guided flow with AVVIA) -->
+          {% if current_user and 'Maker' in current_user.get('roles', []) %}
           <div class="shrink-0 sm:ml-4">
             <a href="{{ url_for('measure.task_execute', task_id=task.id) }}"
                class="btn btn-primary gap-2 w-full sm:w-auto justify-center
@@ -202,6 +203,7 @@
               </svg>
             </a>
           </div>
+          {% endif %}
         </div>
       </div>
     </div>