fix(contracts): 修复合同状态枚举 EXPIRED -> UNSIGNED_TIMEOUT

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/planting-service/src/api/controllers/contract-admin.controller.ts

@@ -242,7 +242,7 @@ export class ContractAdminController {
           status: { in: [ContractSigningStatus.PENDING, ContractSigningStatus.SCROLLED, ContractSigningStatus.ACKNOWLEDGED] },
         },
       }),
-      this.prisma.contractSigningTask.count({ where: { ...where, status: ContractSigningStatus.EXPIRED } }),
+      this.prisma.contractSigningTask.count({ where: { ...where, status: ContractSigningStatus.UNSIGNED_TIMEOUT } }),
     ]);
 
     return {