feat(ops): 添加自动刷新配置功能

功能特性：
- 支持配置启用/禁用自动刷新
- 可配置刷新间隔（15秒/30秒/60秒）
- 实时倒计时显示，用户可见下次刷新时间
- 手动刷新自动重置倒计时
- 页面卸载时自动清理定时器

用户体验：
- 默认禁用，用户可根据需求开启
- 与现有 OpsConcurrencyCard 5秒刷新保持一致
- 倒计时带旋转动画，视觉反馈清晰
- 配置修改后立即生效，无需刷新页面

技术实现：
- ops.ts: 添加 auto_refresh_enabled 和 auto_refresh_interval_seconds 配置
- OpsSettingsDialog.vue: 添加自动刷新配置界面
- OpsDashboard.vue: 实现主刷新逻辑和双定时器设计
- OpsDashboardHeader.vue: 倒计时显示组件

配置说明：
- auto_refresh_enabled: 是否启用（默认 false）
- auto_refresh_interval_seconds: 刷新间隔（默认 30 秒，范围 15-300 秒）

frontend/src/views/admin/ops/OpsDashboard.vue

@@ -20,6 +20,8 @@
         :loading="loading"
         :last-updated="lastUpdated"
         :thresholds="metricThresholds"
+        :auto-refresh-enabled="autoRefreshEnabled"
+        :auto-refresh-countdown="autoRefreshCountdown"
         @update:time-range="onTimeRangeChange"
         @update:platform="onPlatformChange"
         @update:group="onGroupChange"
@@ -104,7 +106,7 @@
 
 <script setup lang="ts">
 import { computed, onMounted, onUnmounted, ref, watch } from 'vue'
-import { useDebounceFn } from '@vueuse/core'
+import { useDebounceFn, useIntervalFn } from '@vueuse/core'
 import { useI18n } from 'vue-i18n'
 import { useRoute, useRouter } from 'vue-router'
 import AppLayout from '@/components/layout/AppLayout.vue'
@@ -287,6 +289,45 @@ const requestDetailsPreset = ref<OpsRequestDetailsPreset>({
 const showSettingsDialog = ref(false)
 const showAlertRulesCard = ref(false)
 
+// Auto refresh settings
+const autoRefreshEnabled = ref(false)
+const autoRefreshIntervalMs = ref(30000) // default 30 seconds
+const autoRefreshCountdown = ref(0)
+
+// Auto refresh timer
+const { pause: pauseAutoRefresh, resume: resumeAutoRefresh, isActive: isAutoRefreshActive } = useIntervalFn(
+  () => {
+    if (autoRefreshEnabled.value && opsEnabled.value && !loading.value) {
+      fetchData()
+    }
+  },
+  autoRefreshIntervalMs,
+  { immediate: false }
+)
+
+// Countdown timer (updates every second)
+const { pause: pauseCountdown, resume: resumeCountdown } = useIntervalFn(
+  () => {
+    if (autoRefreshEnabled.value && autoRefreshCountdown.value > 0) {
+      autoRefreshCountdown.value--
+    }
+  },
+  1000,
+  { immediate: false }
+)
+
+// Load auto refresh settings from backend
+async function loadAutoRefreshSettings() {
+  try {
+    const settings = await opsAPI.getAdvancedSettings()
+    autoRefreshEnabled.value = settings.auto_refresh_enabled
+    autoRefreshIntervalMs.value = settings.auto_refresh_interval_seconds * 1000
+    autoRefreshCountdown.value = settings.auto_refresh_interval_seconds
+  } catch (err) {
+    console.error('[OpsDashboard] Failed to load auto refresh settings', err)
+  }
+}
+
 function handleThroughputSelectPlatform(nextPlatform: string) {
   platform.value = nextPlatform || ''
   groupId.value = null
@@ -510,6 +551,10 @@ async function fetchData() {
     ])
     if (fetchSeq !== dashboardFetchSeq) return
     lastUpdated.value = new Date()
+    // Reset auto refresh countdown after successful fetch
+    if (autoRefreshEnabled.value) {
+      autoRefreshCountdown.value = Math.floor(autoRefreshIntervalMs.value / 1000)
+    }
   } catch (err) {
     if (!isOpsDisabledError(err)) {
       console.error('[ops] failed to fetch dashboard data', err)
@@ -567,9 +612,18 @@ onMounted(async () => {
   // Load thresholds configuration
   loadThresholds()
 
+  // Load auto refresh settings
+  await loadAutoRefreshSettings()
+
   if (opsEnabled.value) {
     await fetchData()
   }
+
+  // Start auto refresh if enabled
+  if (autoRefreshEnabled.value) {
+    resumeAutoRefresh()
+    resumeCountdown()
+  }
 })
 
 async function loadThresholds() {
@@ -584,5 +638,27 @@ async function loadThresholds() {
 
 onUnmounted(() => {
   abortDashboardFetch()
+  pauseAutoRefresh()
+  pauseCountdown()
+})
+
+// Watch auto refresh settings changes
+watch(autoRefreshEnabled, (enabled) => {
+  if (enabled) {
+    autoRefreshCountdown.value = Math.floor(autoRefreshIntervalMs.value / 1000)
+    resumeAutoRefresh()
+    resumeCountdown()
+  } else {
+    pauseAutoRefresh()
+    pauseCountdown()
+    autoRefreshCountdown.value = 0
+  }
+})
+
+// Reload auto refresh settings after settings dialog is closed
+watch(showSettingsDialog, async (show) => {
+  if (!show) {
+    await loadAutoRefreshSettings()
+  }
 })
 </script>