修复生成图片OSS签名缓存链路

前端将完整阿里云OSS generated 地址归一为 legacy path 后走 read-url 换签。

platform-oss 为 generated 私有对象 PostObject 和 PutObject 写入 immutable Cache-Control。

补齐 shared-contracts 与 api-server 直传票据字段映射。

更新后端、运维文档和 Hermes 团队记忆，明确不使用服务端磁盘缓存兜底。

src/services/assetReadUrlService.test.ts

@@ -140,6 +140,48 @@ describe('assetReadUrlService', () => {
     );
   });
 
+  test('resolveAssetReadUrl exchanges generated Aliyun OSS url for signed url', async () => {
+    vi.spyOn(globalThis, 'fetch').mockResolvedValue(
+      new Response(
+        JSON.stringify({
+          ok: true,
+          data: {
+            read: {
+              objectKey:
+                'generated-puzzle-assets/puzzle-session-1/candidate-1/asset-1/image.png',
+              signedUrl: 'https://signed.example.com/puzzle.png',
+              expiresAt: '2099-01-01T00:10:00Z',
+            },
+          },
+          error: null,
+          meta: {
+            apiVersion: '2026-04-08',
+            routeVersion: '2026-04-08',
+            latencyMs: 1,
+            timestamp: '2099-01-01T00:00:00Z',
+          },
+        }),
+        {
+          status: 200,
+          headers: {
+            'Content-Type': 'application/json',
+          },
+        },
+      ),
+    );
+
+    await expect(
+      resolveAssetReadUrl(
+        'https://genarrative-release.oss-cn-beijing.aliyuncs.com/generated-puzzle-assets/puzzle-session-1/candidate-1/asset-1/image.png',
+      ),
+    ).resolves.toBe('https://signed.example.com/puzzle.png');
+
+    expect(globalThis.fetch).toHaveBeenCalledTimes(1);
+    expect(String(vi.mocked(globalThis.fetch).mock.calls[0]?.[0])).toContain(
+      'legacyPublicPath=%2Fgenerated-puzzle-assets%2Fpuzzle-session-1%2Fcandidate-1%2Fasset-1%2Fimage.png',
+    );
+  });
+
   test('resolveAssetReadUrl does not append cache busting query to OSS signed url', async () => {
     vi.spyOn(globalThis, 'fetch').mockResolvedValue(
       new Response(