feat(ops): v4.0.7 HQ 活动图快链与勾选导出

HQ 指定一张活动图为勾选主合伙人合成 PNG/zip；城市合伙人页增加快链与单下/导出。

Co-authored-by: Cursor <cursoragent@cursor.com>

server/dukang-api/src/modules/store/partner-assoc.service.ts

@@ -452,4 +452,19 @@ export class PartnerAssocService {
     const buffer = Buffer.from(await res.arrayBuffer());
     return { buffer, fileName: `partner-assoc-${summary.partnerId}.png` };
   }
+
+  /** 只读已有 OSS 关联码，不调微信补码。无码返回 null。 */
+  async getExistingQrcodeBuffer(partnerAccountId: bigint): Promise<{ buffer: Buffer; fileName: string } | null> {
+    const primary = await this.partnerCityService.resolvePrimaryAccount(partnerAccountId);
+    if (!primary.assocQrcodeResourceId) return null;
+    const resource = await this.prisma.commonResource.findUnique({
+      where: { id: primary.assocQrcodeResourceId },
+      select: { url: true },
+    });
+    if (!resource?.url) return null;
+    const res = await fetch(resource.url);
+    if (!res.ok) return null;
+    const buffer = Buffer.from(await res.arrayBuffer());
+    return { buffer, fileName: `partner-assoc-${primary.id.toString()}.png` };
+  }
 }