refactor(品牌工具页): 抽取 formatDateTime 与 uploadPathsToJava 公共工具

- 新增 shared/utils/datetime.ts：13 个品牌页逐字重复的 formatDateTime 收敛为一处；
  语义不同的 3 个变体（toLocaleString / 字符串切片 / 支持时间戳）保留不动
- 新增 shared/utils/upload-to-java.ts：10 个品牌页的上传循环收敛，api 依赖注入便于单测；
  保留 uploadOss（品牌Tab）与 returnEmptyWhenUnavailable（跟价）两处行为差异
- 补 datetime / upload-to-java 单测 10 例

净减约 327 行；vue-tsc 构建与 690 个前端单测全通过

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

@@ -191,7 +191,7 @@ import ModuleTemplateDownload from '@/shared/components/ModuleTemplateDownload.v
 import TaskCenterPanel from '@/shared/components/tasks/TaskCenterPanel.vue'
 import type { TaskItemView, TaskStatCard } from '@/shared/components/tasks/types'
 import ZiniaoVersionSetting from '@/shared/components/ZiniaoVersionSetting.vue'
-import { expandBrandFolderRecursive, type BrandExpandFolderItem } from '@/shared/api/brand'
+import { expandBrandFolderRecursive } from '@/shared/api/brand'
 import {
   activatePublishFile,
   activatePublishTask,
@@ -219,6 +219,7 @@ import {
 } from '@/shared/dispatch-guard'
 import { passGuard } from '@/shared/dispatch-guard-ui'
 import { useZiniaoVersion, type ZiniaoVersion } from '@/shared/utils/ziniao-version'
+import { uploadPathsToJava } from '@/shared/utils/upload-to-java'
 
 const COUNTRY_OPTIONS = [
   { code: 'DE', label: '德国' },
@@ -476,22 +477,6 @@ function onSyncCountryChange(code: string, event: Event) {
   syncCountries.value = COUNTRY_OPTIONS.map((item) => item.code).filter((item) => selected.has(item))
 }
 
-async function uploadPathsToJava(paths: Array<string | BrandExpandFolderItem>) {
-  const api = getPywebviewApi()
-  if (!api?.upload_file_to_java) throw new Error('当前桌面端未提供文件上传能力')
-  const uploaded: UploadedJavaFile[] = []
-  for (const item of paths) {
-    const filePath = typeof item === 'string' ? item : item.absolutePath
-    const relativePath = typeof item === 'string' ? undefined : item.relativePath
-    const result = await api.upload_file_to_java(filePath, relativePath)
-    if (!result?.success || !result.data) {
-      throw new Error(result?.error || result?.message || `上传失败：${filePath}`)
-    }
-    uploaded.push(result.data)
-  }
-  return uploaded
-}
-
 async function selectFiles() {
   const api = getPywebviewApi()
   if (!api?.select_brand_xlsx_files || !api.upload_file_to_java) {
@@ -503,7 +488,7 @@ async function selectFiles() {
     if (!paths?.length) return
     if (!(await passGuard(checkSelectedFiles(paths, { allowedExtensions: EXCEL_EXTENSIONS })))) return
     uploading.value = true
-    const uploaded = await uploadPathsToJava(paths)
+    const uploaded = await uploadPathsToJava(getPywebviewApi(), paths)
     selectedPaths.value = paths
     uploadedFiles.value = uploaded
     ElMessage.success(`已上传 ${uploaded.length} 个待上架文件`)
@@ -533,7 +518,7 @@ async function selectFolder() {
     }
     if (!(await passGuard(checkSelectedFiles(result.items, { allowedExtensions: EXCEL_EXTENSIONS })))) return
     uploading.value = true
-    const uploaded = await uploadPathsToJava(result.items)
+    const uploaded = await uploadPathsToJava(getPywebviewApi(), result.items)
     selectedPaths.value = result.items.map((item) => item.relativePath || item.absolutePath)
     uploadedFiles.value = uploaded
     ElMessage.success(`已上传文件夹内 ${uploaded.length} 个 xlsx 文件`)