feat(api): album asset upload chain

P1b Task 3: initAlbumAssetUpload / completeAlbumAssetUpload (tags
[assets]) over album_assets with in-row one-shot sessions.

- migration asset_state: album_assets + state (pending|effective),
  expectedBytes, contentType (utf8mb4_0900_bin); pre-existing rows
  backfilled to effective. Complete head-verifies bytes AND
  contentType vs the init declaration (P1a Task 11 server-side
  fallback), then conditionally flips pending->effective with the
  winner writing the album.asset.add audit (resourceId=albumId,
  metadata assetId/kind/locale). Effective rows re-complete
  idempotently (re-signed URL, no re-verify, survives object
  cleanup).
- object key is the final key (albums/{albumId}/assets/{assetId}.{ext});
  the pending row is the logical staging - no copy step, keys embed
  assetId so re-init can never overwrite another row's object.
- permissions: owner/admin only (collaborator 403, outsider 404);
  uploadEnabled does NOT gate assets (switch governs photo uploads
  per 4.9 - both endpoints carry no ALBUM_UPLOAD_DISABLED).
- public banner now locale-aware (req 4.7): effective rows resolved
  as display-locale row -> global (locale NULL) row -> null, latest
  wins per tier (same-kind re-upload replaces, old rows retained).
- e2e: test/assets.e2e-spec.ts (14 cases, real jpegs via sharp,
  MinIO round-trips); public spec seed marked effective.

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

services/api/src/public/public.service.ts

@@ -9,8 +9,10 @@
 //     决策），与缺省同样走回退；resolvedLocale 向客户端指示实际返回语言。
 //   · 分类名称同语言解析：resolved locale → defaultLocale → 任一既有条目
 //     （确定性：locale 升序取首）；分类创建必附翻译，末级分支纯防御。
-//   · banner：album_assets(kind=banner) 多行时取最新一条（createdAt DESC,
-//     id DESC 决胜）；P1a 无按语言选封面概念（locale 列为 P1b 上传链路预留）。
+//   · banner（P1b Task 3 起对接上传链路）：album_assets(kind=banner,
+//     state='effective') 中按语言偏好解析（需求 4.7）——resolved locale 行 →
+//     全局行（locale NULL）→ null；同级取最新（createdAt,id DESC 决胜，同
+//     (kind, locale) 再上传即替换语义）。
 //   · 签名 URL 一律现签（SIGNED_URL_TTL_SECONDS 惰性读取，SigV4 本地计算无
 //     网络副作用）；单图定位端点是契约规定的过期刷新入口。
 //   · viewCount：P1a 占位 null（§7.1 /visits 端点后续提供）。
@@ -100,15 +102,22 @@ export class PublicService {
       bucket.set(row.locale, row.name);
     }
 
-    // banner：最新 banner 资产行现签（无行 → null）。
-    const bannerAsset = await this.prisma.album_assets.findFirst({
-      where: { albumId: album.id, kind: 'banner' },
+    // banner（P1b Task 3 起对接上传链路）：仅 state='effective' 行参与；语言
+    // 偏好解析（需求 4.7）——resolved locale 行 → 全局行（locale NULL）→ null。
+    // 以「实际展示语言」（translation 解析结果）为偏好驱动：banner 跟随观众
+    // 看到的文案语言，而非原始请求值（请求 fr 回退 zh 时配 zh banner）。
+    // 同级多行取最新（createdAt,id DESC 决胜）：同 (kind, locale) 再上传即替换
+    // 语义——新行生效、旧行保留，此处取最新 effective 行。
+    const bannerAssets = await this.prisma.album_assets.findMany({
+      where: { albumId: album.id, kind: 'banner', state: 'effective' },
       orderBy: [{ createdAt: 'desc' }, { id: 'desc' }],
     });
+    const bannerRow =
+      bannerAssets.find((row) => row.locale === resolved.locale) ??
+      bannerAssets.find((row) => row.locale === null) ??
+      null;
     const banner =
-      bannerAsset === null
-        ? null
-        : await this.presign(bannerAsset.objectKey);
+      bannerRow === null ? null : await this.presign(bannerRow.objectKey);
 
     return {
       publicToken: album.publicToken,