feat(wm-revenue): #52 电子发票管理+应收应付账务+欠费催缴
- Entity: Invoice, Receivable, Payable, Reconciliation, CollectionRecord
- Mapper: 5个MyBatis-Plus Mapper接口
- Service: InvoiceService(开具/查询/推送/红冲), AccountService(应收/应付/对账/结转), CollectionService(催缴/通知/统计)
- Controller: InvoiceController(8端点), AccountController(12端点), CollectionController(8端点)
- DDL: V_invoice_account.sql(5张表+索引)
- Test: InvoiceAccountTest(16个测试用例)
