refactor(ops): 优化任务心跳和组件刷新机制

后端改动:
- 添加 ops_job_heartbeats.last_result 字段记录任务执行结果
- 优化告警评估器统计信息(规则数/事件数/邮件数)
- 统一各定时任务的心跳记录格式

前端改动:
- 重构 OpsConcurrencyCard 使用父组件统一控制刷新节奏
- 移除独立的 5 秒刷新定时器,改用 refreshToken 机制
- 修复 TypeScript 类型错误

frontend/src/views/admin/AccountsView.vue

@@ -414,7 +414,7 @@ const handleScroll = () => {
   menu.show = false
 }
 
-onMounted(async () => { load(); try { const [p, g] = await Promise.all([adminAPI.proxies.getAll(), adminAPI.groups.getAll()]); proxies.value = p; groups.value = g } catch (error) { console.error('Failed to load proxies/groups:', error) }; window.addEventListener('scroll', handleScroll, true) })
+onMounted(async () => { load(); try { const [p, g] = await Promise.all([adminAPI.proxies.getAll(), adminAPI.groups.getAll()]); proxies.value = p; groups.value = g } catch (error) { console.error('Failed to load proxies/groups:', error) } window.addEventListener('scroll', handleScroll, true) })
 
 onUnmounted(() => {
   window.removeEventListener('scroll', handleScroll, true)