feat: 配置功能仅admin可用，operator隐藏配置按钮+后端403拦截

- devices.html: 注入 USER_ROLE 全局变量
- devices.js: 配置按钮仅 USER_ROLE===admin 时渲染
- fixture.py: 页面/指令/保存三个路由均校验 admin 角色

edc-web/app/static/js/devices.js

@@ -22,7 +22,7 @@ function renderTable(devices) {
             <td>${d.last_login || '-'}</td>
             <td>
                 <button class="btn-test" onclick="location.href='/test/${d.id}'">测试</button>
-                <button class="btn-config" onclick="location.href='/fixture/${d.id}'">配置</button>
+                ${USER_ROLE === 'admin' ? `<button class="btn-config" onclick="location.href='/fixture/${d.id}'">配置</button>` : ''}
             </td>
         </tr>
     `).join("");