fix(planting-service): 添加 P2002 错误捕获处理并发创建冲突

PostgreSQL 的 upsert 在高并发下仍可能出现唯一约束错误，
添加 try-catch 捕获 P2002 错误，发生冲突时直接查询返回已存在的记录。

🤖 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

@@ -43,31 +43,51 @@ export class ContractSigningTaskRepositoryImpl implements IContractSigningTaskRe
     } 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）
-      const result = await this.prisma.contractSigningTask.upsert({
-        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);
+      // 额外捕获 P2002 错误以处理极端并发情况
+      try {
+        const result = await this.prisma.contractSigningTask.upsert({
+          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);
+          }
+        }
+        throw error;
+      }
     }
   }