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/tests/upload-to-java.test.ts

@@ -0,0 +1,70 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { uploadPathsToJava } from '../src/shared/utils/upload-to-java.ts'
+import type { PywebviewApi } from '../src/shared/bridges/pywebview.ts'
+
+function fakeApi(
+  upload: (
+    filePath: string,
+    relativePath?: string,
+    uploadOss?: boolean,
+  ) => Promise<{ success: boolean; data?: never; error?: string; message?: string }>,
+) {
+  return { upload_file_to_java: upload } as unknown as PywebviewApi
+}
+
+function okData(filePath: string) {
+  return { fileKey: `k:${filePath}`, originalFilename: filePath, localPath: '', size: 1 }
+}
+
+test('uploadPathsToJava 逐个上传并返回结果列表', async () => {
+  const calls: Array<[string, string | undefined, boolean | undefined]> = []
+  const api = fakeApi(async (filePath, relativePath, uploadOss) => {
+    calls.push([filePath, relativePath, uploadOss])
+    return { success: true, data: okData(filePath) as never }
+  })
+
+  const result = await uploadPathsToJava(api, ['/a.xlsx', { absolutePath: '/b.xlsx', relativePath: 'sub/b.xlsx' }])
+
+  assert.equal(result.length, 2)
+  assert.deepEqual(calls, [
+    ['/a.xlsx', undefined, undefined],
+    ['/b.xlsx', 'sub/b.xlsx', undefined],
+  ])
+})
+
+test('uploadPathsToJava 透传 uploadOss 参数', async () => {
+  let seen: boolean | undefined
+  const api = fakeApi(async (filePath, _relativePath, uploadOss) => {
+    seen = uploadOss
+    return { success: true, data: okData(filePath) as never }
+  })
+
+  await uploadPathsToJava(api, ['/a.xlsx'], { uploadOss: true })
+
+  assert.equal(seen, true)
+})
+
+test('uploadPathsToJava 任一失败即整体抛错并带上桥返回的文案', async () => {
+  const api = fakeApi(async (filePath) =>
+    filePath === '/bad.xlsx'
+      ? { success: false, error: '磁盘读取失败' }
+      : { success: true, data: okData(filePath) as never },
+  )
+
+  await assert.rejects(() => uploadPathsToJava(api, ['/ok.xlsx', '/bad.xlsx']), /磁盘读取失败/)
+})
+
+test('uploadPathsToJava 失败无文案时回落到「上传失败：路径」', async () => {
+  const api = fakeApi(async () => ({ success: false }))
+
+  await assert.rejects(() => uploadPathsToJava(api, ['/x.xlsx']), /上传失败：\/x\.xlsx/)
+})
+
+test('uploadPathsToJava 缺上传桥默认抛错', async () => {
+  await assert.rejects(() => uploadPathsToJava(undefined, ['/a.xlsx']), /未提供文件上传能力/)
+})
+
+test('uploadPathsToJava 缺上传桥时 returnEmptyWhenUnavailable 返回空数组', async () => {
+  assert.deepEqual(await uploadPathsToJava(undefined, ['/a.xlsx'], { returnEmptyWhenUnavailable: true }), [])
+})