task-85: 优化 Similar ASIN 轮询与文件生成等待，避免重复 force 请求

新增纯 TS force 节流守卫 asin-force-throttle：为每个 taskId 维护 TTL
冷却窗口，窗口内不重复发 force 请求（避免反复触发后端生成文件），到期
后允许重试，任务终态后 clear 立即释放记录。BrandSimilarAsinTab 的
refreshTaskProgress 改为按 pendingFileTaskIds 逐项查守卫决定本轮是否
带 force，请求成功后整批进入冷却。8 个测试覆盖默认、批量、幂等、空、
单元素、200 任务溢出、非法输入与时钟故障恢复。

frontend-vue/src/pages/brand/components/BrandSimilarAsinTab.vue

@@ -211,6 +211,7 @@ import { getTaskPollIntervalMs } from '@/shared/task-progress-config'
 import { getStoredApiSecret } from '@/shared/utils/api-secret-store'
 import { createCategorizedTimers } from '@/shared/utils/categorized-timers'
 import { saveUrlWithProgress } from '@/shared/utils/download-progress'
+import { createAsinForceThrottle } from '@/shared/asin-force-throttle'
 
 const selectedFileNames = ref<string[]>([])
 const uploadedFiles = ref<UploadFileVo[]>([])
@@ -228,6 +229,8 @@ const pollingTaskIds = ref<number[]>([])
 const pendingFileTaskIds = ref<number[]>([])
 const pollTimer = ref<number | null>(null)
 const pollingInFlight = ref(false)
+// force 请求节流：文件生成中不重复 force（TTL 窗口内只发一次），终态后 clear 释放
+const forceThrottle = createAsinForceThrottle({ ttlMs: 30_000 })
 const HISTORY_CACHE_TTL_MS = 3000
 let historyInFlight: Promise<void> | null = null
 let lastHistoryLoadedAt = 0
@@ -608,6 +611,7 @@ function addPendingFileTask(taskId: number) {
 
 function removePendingFileTask(taskId: number) {
   pendingFileTaskIds.value = pendingFileTaskIds.value.filter((id) => id !== taskId)
+  forceThrottle.clear(taskId)
   if (!pollingTaskIds.value.includes(taskId)) {
     const next = { ...liveProgressItems.value }
     delete next[taskId]
@@ -683,7 +687,12 @@ async function refreshTaskProgress() {
     let shouldRefreshHistory = false
     const taskIds = Array.from(new Set([...pollingTaskIds.value, ...pendingFileTaskIds.value]))
     if (taskIds.length) {
-      const batch = await getSimilarAsinTaskProgressBatch(taskIds, { force: pendingFileTaskIds.value.length > 0 })
+      const force = pendingFileTaskIds.value.some((taskId) => forceThrottle.shouldForce(taskId))
+      const batch = await getSimilarAsinTaskProgressBatch(taskIds, { force })
+      if (force) {
+        // force 请求已发出，进入冷却窗口；TTL 内不再重复 force，避免重复触发文件生成
+        pendingFileTaskIds.value.forEach((taskId) => forceThrottle.markForce(taskId))
+      }
       for (const detail of batch.items || []) {
         const task = detail.task
         if (!task?.id) continue