fix(planting-service): 修复合同签署任务创建的并发问题

- 将 upsert 改为 create + 重试机制
- 处理 P2002 唯一约束冲突时使用指数退避重试
- 确保并发创建时能正确返回已存在的记录

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/services/planting-service/src/infrastructure/persistence/repositories/contract-signing-task.repository.impl.ts

@@ -42,53 +42,68 @@ export class ContractSigningTaskRepositoryImpl implements IContractSigningTaskRe
       });
       return this.mapToDomain(updated);
     } else {
-      // 创建 - 使用 upsert 处理并发幂等性
-      // 如果 orderNo 已存在，则只返回现有记录（不更新）
-      // 额外捕获 P2002 错误以处理极端并发情况
-      try {
-        const result = await this.prisma.contractSigningTask.upsert({
+      // 创建 - 使用重试机制处理并发幂等性
+      // 先尝试查询，如果不存在再创建，如果创建失败（并发冲突）则重新查询
+      const maxRetries = 3;
+      for (let attempt = 1; attempt <= maxRetries; attempt++) {
+        // 先检查是否已存在
+        const existing = await this.prisma.contractSigningTask.findUnique({
           where: { orderNo: task.orderNo },
-          create: {
-            orderNo: task.orderNo,
-            userId: task.userId,
-            accountSequence: task.accountSequence,
-            templateId: task.templateId,
-            contractVersion: task.contractVersion,
-            contractContent: task.contractContent,
-            userPhoneNumber: task.userPhoneNumber,
-            userRealName: task.userRealName,
-            userIdCardNumber: task.userIdCardNumber,
-            treeCount: task.treeCount,
-            totalAmount: new Prisma.Decimal(task.totalAmount),
-            provinceCode: task.provinceCode,
-            provinceName: task.provinceName,
-            cityCode: task.cityCode,
-            cityName: task.cityName,
-            status: task.status,
-            expiresAt: task.expiresAt,
-          },
-          // 如果已存在，不更新任何字段，只返回现有记录
-          update: {},
         });
-        return this.mapToDomain(result);
-      } catch (error: unknown) {
-        // 处理并发创建时的唯一约束冲突 (Prisma P2002)
-        if (
-          error &&
-          typeof error === 'object' &&
-          'code' in error &&
-          error.code === 'P2002'
-        ) {
-          // 记录已被其他并发请求创建，直接查询返回
-          const existing = await this.prisma.contractSigningTask.findUnique({
-            where: { orderNo: task.orderNo },
-          });
-          if (existing) {
-            return this.mapToDomain(existing);
-          }
+        if (existing) {
+          return this.mapToDomain(existing);
+        }
+
+        try {
+          // 尝试创建
+          const result = await this.prisma.contractSigningTask.create({
+            data: {
+              orderNo: task.orderNo,
+              userId: task.userId,
+              accountSequence: task.accountSequence,
+              templateId: task.templateId,
+              contractVersion: task.contractVersion,
+              contractContent: task.contractContent,
+              userPhoneNumber: task.userPhoneNumber,
+              userRealName: task.userRealName,
+              userIdCardNumber: task.userIdCardNumber,
+              treeCount: task.treeCount,
+              totalAmount: new Prisma.Decimal(task.totalAmount),
+              provinceCode: task.provinceCode,
+              provinceName: task.provinceName,
+              cityCode: task.cityCode,
+              cityName: task.cityName,
+              status: task.status,
+              expiresAt: task.expiresAt,
+            },
+          });
+          return this.mapToDomain(result);
+        } catch (error: unknown) {
+          // 处理并发创建时的唯一约束冲突 (Prisma P2002)
+          if (
+            error &&
+            typeof error === 'object' &&
+            'code' in error &&
+            error.code === 'P2002'
+          ) {
+            // 记录已被其他并发请求创建，等待一小段时间后重试查询
+            if (attempt < maxRetries) {
+              await new Promise((resolve) => setTimeout(resolve, 50 * attempt));
+              continue;
+            }
+            // 最后一次尝试查询
+            const finalExisting = await this.prisma.contractSigningTask.findUnique({
+              where: { orderNo: task.orderNo },
+            });
+            if (finalExisting) {
+              return this.mapToDomain(finalExisting);
+            }
+          }
+          throw error;
         }
-        throw error;
       }
+      // 不应该到达这里，但为了类型安全
+      throw new Error(`Failed to create or find signing task after ${maxRetries} attempts`);
     }
   }