feat: 完善媒体管理与备份迁移流程

- 视频上传生成缩略图并提供占位封面和失败原因展示
- 支持 HLS 按需重新封装 MP4，并限制临时文件生命周期与访问权限
- 完善视频、文件 API 文档、搜索、批量删除和单次转码质量参数
- 修复备份恢复与跨后端迁移遗漏缩略图、HLS 清单和分片的问题
- 将备份任务、归档和下载权限按用户隔离
- 增加仅清理当前用户数据的高危存储清空流程和二次文字确认
- 修复 S3 中文文件名元数据及 CLI 数据库连接问题
- 补充备份恢复、用户隔离、媒体资源和转码相关测试

server/api/admin/backup/estimate.get.ts

@@ -1,12 +1,23 @@
 import { requireAdminAuth } from '../../../utils/access'
 import { getBackupExportEstimate } from '../../../utils/backup/stats'
 import { getBackupsDir, isSafeBackupFilename } from '../../../utils/backup/paths'
+import { listAllBackupJobsForUser } from '../../../utils/backup/jobs'
+import { basename, join } from 'node:path'
 import { promises as fs } from 'node:fs'
-import { join } from 'node:path'
 
 export default defineEventHandler(async (event) => {
-  await requireAdminAuth(event)
+  const user = await requireAdminAuth(event)
   const estimate = await getBackupExportEstimate()
+  const allowedArchives = new Set(
+    listAllBackupJobsForUser(user.id).flatMap((job) => {
+      const names: string[] = []
+      if (job.outputPath) names.push(basename(job.outputPath))
+      if (typeof job.payload.archivePath === 'string') {
+        names.push(basename(job.payload.archivePath))
+      }
+      return names
+    })
+  )
 
   const packages = await (async () => {
     try {
@@ -15,6 +26,7 @@ export default defineEventHandler(async (event) => {
       const items = await Promise.all(
         entries
           .filter(entry => entry.isFile() && isSafeBackupFilename(entry.name))
+          .filter(entry => allowedArchives.has(entry.name))
           .map(async (entry) => {
             const full = join(getBackupsDir(), entry.name)
             const fileStat = await fs.stat(full)