perf(frontend): 收敛导航预取并去重首屏请求

- 导航预取仅保留 pointerdown 触发，移除 mouseenter/focus，避免鼠标划过误触发
- 后台预取只做组件懒加载，不再预取各页业务数据，减少首屏资源争抢
- 版本状态检查增加 sessionStorage 缓存（正常 20 分钟 / 错误 5 分钟 TTL）
- fetchModules、必读公告拉取增加请求去重，避免并发重复请求
- 更新检查改用可清理的定时器，组件卸载时清理
- UsageRecordsTable 搜索防抖改为自定义实现，卸载时取消挂起 emit 并补充测试

frontend/src/features/usage/components/UsageRecordsTable.vue

@@ -1057,8 +1057,8 @@
 </template>
 
 <script setup lang="ts">
-import { ref, computed, watch } from 'vue'
-import { useDebounceFn, useLocalStorage } from '@vueuse/core'
+import { ref, computed, onBeforeUnmount, watch } from 'vue'
+import { useLocalStorage } from '@vueuse/core'
 import {
   TableCard,
   Badge,
@@ -1355,10 +1355,26 @@ const timeRangeModel = computed({
 })
 
 // 通用搜索（输入防抖）
+const SEARCH_EMIT_DEBOUNCE_MS = 300
 const localSearch = ref(props.filterSearch)
-const emitSearchDebounced = useDebounceFn((value: string) => {
-  emit('update:filterSearch', value)
-}, 300)
+let searchEmitTimer: ReturnType<typeof setTimeout> | null = null
+
+function cancelPendingSearchEmit() {
+  if (searchEmitTimer !== null) {
+    clearTimeout(searchEmitTimer)
+    searchEmitTimer = null
+  }
+}
+
+function scheduleSearchEmit(value: string) {
+  cancelPendingSearchEmit()
+  searchEmitTimer = setTimeout(() => {
+    searchEmitTimer = null
+    if (value !== props.filterSearch) {
+      emit('update:filterSearch', value)
+    }
+  }, SEARCH_EMIT_DEBOUNCE_MS)
+}
 
 function getDisplayStatus(record: UsageRecord) {
   return resolveDisplayRequestStatus(record)
@@ -1422,12 +1438,18 @@ function formatRecordProviderSegment(record: UsageRecord): string {
 
 watch(() => props.filterSearch, (value) => {
   if (value !== localSearch.value) {
+    cancelPendingSearchEmit()
     localSearch.value = value
   }
 })
 
 watch(localSearch, (value) => {
-  emitSearchDebounced(value)
+  if (value === props.filterSearch) return
+  scheduleSearchEmit(value)
+})
+
+onBeforeUnmount(() => {
+  cancelPendingSearchEmit()
 })
 
 // 使用复用的行点击逻辑

frontend/src/features/usage/components/__tests__/UsageRecordsTable.spec.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest'
-import { createApp, defineComponent, h, type App } from 'vue'
+import { createApp, defineComponent, h, nextTick, type App } from 'vue'
 import UsageRecordsTable from '../UsageRecordsTable.vue'
 import type { UsageRecord } from '../../types'
 
@@ -167,6 +167,7 @@ afterEach(() => {
     app.unmount()
     root.remove()
   }
+  vi.useRealTimers()
 })
 
 describe('UsageRecordsTable', () => {
@@ -314,6 +315,31 @@ describe('UsageRecordsTable', () => {
     expect(onUpdateHideUnknownRecords).toHaveBeenCalledWith(true)
   })
 
+  it('debounces usage search updates', async () => {
+    vi.useFakeTimers()
+    const onUpdateFilterSearch = vi.fn()
+    const root = mountUsageRecordsTable([buildRecord()], {
+      'onUpdate:filterSearch': onUpdateFilterSearch,
+    })
+    const input = root.querySelector<HTMLInputElement>('#usage-records-search')
+    expect(input).not.toBeNull()
+
+    input!.value = 'a'
+    input!.dispatchEvent(new Event('input'))
+    input!.value = 'ab'
+    input!.dispatchEvent(new Event('input'))
+    input!.value = 'abc'
+    input!.dispatchEvent(new Event('input'))
+    await nextTick()
+
+    await vi.advanceTimersByTimeAsync(299)
+    expect(onUpdateFilterSearch).not.toHaveBeenCalled()
+
+    await vi.advanceTimersByTimeAsync(1)
+    expect(onUpdateFilterSearch).toHaveBeenCalledTimes(1)
+    expect(onUpdateFilterSearch).toHaveBeenCalledWith('abc')
+  })
+
   it('shows retry and fallback markers together when both flags are set', () => {
     const root = mountUsageRecordsTable([buildRecord({
       has_fallback: true,