feat(server): 站内通知基础设施与关键事件触发(F14,F30)

- 新增 notifications 表与 API(list/mark-read)
- submit/approve/reject/return/transfer/pay/forgot-password 写入站内通知
- 通知失败降级，不阻塞主流程

server/src/app.js

@@ -26,6 +26,7 @@ const departmentsRoutes = require("./routes/departments");
 const employeesRoutes = require("./routes/employees");
 const expenseTypesRoutes = require("./routes/expenseTypes");
 const configReadRoutes = require("./routes/configRead");
+const notificationsRoutes = require("./routes/notifications");
 const { startDelegationRevokeJob } = require("./jobs/delegationRevokeJob");
 const { startOcrJob } = require("./jobs/ocrJob");
 const { startInvoiceArchiveJob } = require("./jobs/invoiceArchiveJob");
@@ -200,6 +201,7 @@ async function buildApp() {
   await app.register(departmentsRoutes, { prefix: "/api" });
   await app.register(expenseTypesRoutes, { prefix: "/api" });
   await app.register(configReadRoutes, { prefix: "/api" });
+  await app.register(notificationsRoutes, { prefix: "/api" });
 
   startDelegationRevokeJob(app);
   startOcrJob(app);