feat(wm-dispatch): #60 综合工单管理（创建/分派/处理/完成/统计）
- Entity: WorkOrder(增强), WorkOrderLog, WorkOrderAssignment
- DTO: CreateRequest, QueryRequest, AssignRequest, ProcessRequest, StatVO, BatchAssignRequest, BatchCancelRequest
- Mapper: WorkOrderMapper(增强统计SQL), WorkOrderLogMapper, WorkOrderAssignmentMapper
- Service: WorkOrderLifecycleService(全生命周期), WorkOrderLedgerService(台账查询), WorkOrderStatisticsService(统计分析)
- Controller: WorkOrderController(16个端点)
- DDL: V3__workorder.sql(3张表+索引)
- Test: WorkOrderLifecycleServiceTest(15个), WorkOrderStatisticsServiceTest(3个)
功能特性:
- 工单创建: 支持REPAIR/INSPECTION/COMPLAINT/EMERGENCY四种类型 + LOW/MEDIUM/HIGH/URGENT优先级 + 附件
- 工单分派: 手动/自动分派 + 多人协作(主负责人+协助人)
- 工单处理: 状态流转(待办→已分派→处理中→已完成/已驳回/已取消) + 处理日志
- 工单统计: 完成率/平均处理时长/按类型分布/按优先级分布/按人员分布/逾期数/今日统计
