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/utils/media-assets.test.ts

@@ -0,0 +1,67 @@
+import { describe, expect, it } from 'vitest'
+import { LocalStorageBackend } from './storage/local'
+import type { ImageIndexRow } from './image-index'
+import { collectMediaAssetKeys } from './media-assets'
+
+const row: ImageIndexRow = {
+  key: 'videos/2026/10/example.mp4',
+  backend_id: 'local',
+  user_id: 1,
+  folder: 'videos',
+  original_name: 'example.mp4',
+  content_type: 'video/mp4',
+  size: 100,
+  uploaded_at: '2026-10-17T00:00:00.000Z',
+  hls_key: 'videos/2026/10/example/index.m3u8',
+  transcode_status: 'done',
+  transcode_progress: 100,
+  thumb_key: 'videos/2026/10/example.webp',
+  source_deleted: 0,
+  transcode_preset: 'veryfast',
+  transcode_error: null
+}
+
+async function createBackend() {
+  const backend = new LocalStorageBackend()
+  const meta = {
+    originalName: 'example',
+    uploadedAt: row.uploaded_at,
+    contentType: 'application/octet-stream',
+    size: 0,
+    userId: row.user_id,
+    mediaType: 'video' as const
+  }
+  await backend.put(row.key, new Uint8Array([1]), meta)
+  await backend.put(row.thumb_key!, new Uint8Array([2]), meta)
+  await backend.put(
+    row.hls_key!,
+    new TextEncoder().encode('#EXTM3U\n#EXTINF:6,\nseg000.ts\n'),
+    meta
+  )
+  await backend.put('videos/2026/10/example/seg000.ts', new Uint8Array([3]), meta)
+  return backend
+}
+
+describe('collectMediaAssetKeys', () => {
+  it('includes source, thumbnail, playlist and HLS segments', async () => {
+    const backend = await createBackend()
+    expect(new Set(await collectMediaAssetKeys(row, backend))).toEqual(new Set([
+      row.key,
+      row.thumb_key,
+      row.hls_key,
+      'videos/2026/10/example/seg000.ts'
+    ]))
+  })
+
+  it('omits the source when transcoding already removed it', async () => {
+    const backend = await createBackend()
+    expect(new Set(await collectMediaAssetKeys({
+      ...row,
+      source_deleted: 1
+    }, backend))).toEqual(new Set([
+      row.thumb_key,
+      row.hls_key,
+      'videos/2026/10/example/seg000.ts'
+    ]))
+  })
+})