feat(planting-service): 添加 transfer_locked_count 列的数据库迁移

Prisma schema 中已定义 transferLockedCount 字段但缺少对应 migration，
导致运行时 PrismaClientKnownRequestError:
  The column planting_orders.transfer_locked_count does not exist

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/services/planting-service/prisma/migrations/20260227000000_add_transfer_locked_count/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable: 为认种订单添加转让锁定计数字段
+ALTER TABLE "planting_orders" ADD COLUMN "transfer_locked_count" INTEGER NOT NULL DEFAULT 0;