feat(api): idempotent upload session init with presigned credential

POST /v1/uploads (Task 18, A03): @@unique(userId, clientTaskId) idempotency
anchor — same params return the original session (201, no duplicate photo);
param drift (album/bytes/contentType/extension) -> 409 UPLOAD_SESSION_CONFLICT.
photos.objectKey is set to the FINAL originals key at init while the session
holds the staging key; IDs come from an app-side cuid-like generator so both
self-referencing keys are written in one transaction. Credential is a real
MinIO presigned PUT (SIGNED_URL_TTL_SECONDS, lazily read). Permission order:
album invisible 404 -> member 403 -> uploadEnabled 409 -> size/ext 400 ->
category ownership 400. No audit on init (audit anchors on complete).

Pre-step for Task 19: QUEUE_PHOTO_PROCESS contract constant + lazy-safe
BullMQ queue producer (Redis down at boot must not crash the app; enqueue
failure only logs — sweep compensates). e2e reset now also wipes the MinIO
photo-live/dev prefix; jest maps @photo/storage to TS source.

Co-Authored-By: Claude Code <noreply@anthropic.com>

services/api/src/uploads/dto.ts

@@ -0,0 +1,50 @@
+// services/api/src/uploads/dto.ts —— 上传端点入参 DTO（Task 18）。校验约束对齐
+// 契约 UploadInitRequest：
+//   · contentType 限白名单枚举（image/heic 暂定，G2 真机验证）；
+//   · bytes ≥ 1（契约 minimum）；上限 UPLOAD_MAX_BYTES 是环境相关量，逐请求
+//     惰性读取，故在服务层校验（同 filename 扩展名白名单与 categoryId 属主校验）；
+//   · clientTaskId/filename/albumId/categoryId 列宽对齐 db-cn schema
+//     （VarChar 128/255/64/64）。
+import {
+  IsIn,
+  IsInt,
+  IsNotEmpty,
+  IsOptional,
+  IsString,
+  MaxLength,
+  Min,
+} from 'class-validator';
+import { UPLOAD_CONTENT_TYPES, type UploadContentType } from './support';
+
+export class UploadInitRequestDto {
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(64)
+  albumId!: string;
+
+  /** 缺省为相册默认分类（P1a 无默认分类概念，落 null）。 */
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(64)
+  categoryId?: string;
+
+  /** 客户端任务幂等键（A03：同任务重试复用会话与照片 ID）。 */
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(128)
+  clientTaskId!: string;
+
+  /** 原始文件名，仅元数据；扩展名白名单校验在服务层（对象键后缀派生）。 */
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(255)
+  filename!: string;
+
+  @IsInt()
+  @Min(1)
+  bytes!: number;
+
+  @IsIn(UPLOAD_CONTENT_TYPES)
+  contentType!: UploadContentType;
+}