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/BrandBrandTab.vue

@@ -125,7 +125,8 @@ import { getTaskPollIntervalMs } from '@/shared/task-progress-config'
 import { createCategorizedTimers } from '@/shared/utils/categorized-timers'
 import type { UploadFileVo } from '@/shared/api/upload.ts'
 import type { UploadedFileRef } from '@/shared/api/types/upload.ts'
-import type { BrandExpandFolderItem } from '@/shared/api/types/modules/brand'
+import { formatDateTime } from '@/shared/utils/datetime'
+import { uploadPathsToJava } from '@/shared/utils/upload-to-java'
 
 const uploadedFiles = ref<UploadFileVo[]>([])
 const strategy = ref<'Terms' | 'Simple'>('Simple')
@@ -342,38 +343,7 @@ function toBrandTaskView(item: BrandTaskItem): TaskItemView {
   }
 }
 
-function formatDateTime(value?: string) {
-  if (!value) return '-'
-  const date = new Date(value)
-  if (Number.isNaN(date.getTime())) return value
-  const year = date.getFullYear()
-  const month = String(date.getMonth() + 1).padStart(2, '0')
-  const day = String(date.getDate()).padStart(2, '0')
-  const hours = String(date.getHours()).padStart(2, '0')
-  const minutes = String(date.getMinutes()).padStart(2, '0')
-  const seconds = String(date.getSeconds()).padStart(2, '0')
-  return `${year}-${month}-${day} ${hours}:${minutes}:${seconds}`
-}
-
 /** 上传本地 xlsx 到 Java 临时目录，成功后回填 fileUrl（服务器本地路径，Java 直接读取） */
-async function uploadBrandPathsToJava(paths: Array<string | BrandExpandFolderItem>) {
-  const api = getPywebviewApi()
-  if (!api?.upload_file_to_java) {
-    throw new Error('当前环境未提供文件上传能力')
-  }
-  const files: UploadFileVo[] = []
-  for (const item of paths) {
-    const filePath = typeof item === 'string' ? item : item.absolutePath
-    const relativePath = typeof item === 'string' ? undefined : item.relativePath
-    const uploaded = await api.upload_file_to_java(filePath, relativePath, true)
-    if (!uploaded?.success || !uploaded.data) {
-      throw new Error(uploaded?.error || uploaded?.message || `上传失败：${filePath}`)
-    }
-    files.push(uploaded.data)
-  }
-  return files
-}
-
 async function selectFiles() {
   const bridge = getPywebviewApi()
   if (!bridge?.select_brand_xlsx_files) {
@@ -384,7 +354,7 @@ async function selectFiles() {
   if (!paths?.length) return
   if (!(await passGuard(checkSelectedFiles(paths, { allowedExtensions: EXCEL_EXTENSIONS })))) return
   try {
-    const files = await uploadBrandPathsToJava(paths)
+    const files = await uploadPathsToJava(getPywebviewApi(), paths, { uploadOss: true })
     uploadedFiles.value = files
     ElMessage.success(`已选择并上传 ${files.length} 个 Excel 文件`)
   } catch (error) {
@@ -412,7 +382,7 @@ async function selectFolder() {
       return
     }
     if (!(await passGuard(checkSelectedFiles(res.items.map((i) => i.absolutePath), { allowedExtensions: EXCEL_EXTENSIONS })))) return
-    const files = await uploadBrandPathsToJava(res.items)
+    const files = await uploadPathsToJava(getPywebviewApi(), res.items, { uploadOss: true })
     uploadedFiles.value = files
     ElMessage.success(`已选择并上传文件夹内 ${files.length} 个 Excel 文件`)
   } catch (error) {