feat: 实现统一日志系统和维护模式功能

backend/middleware/maintenance.js

@@ -0,0 +1,31 @@
+const { isMaintenanceModeActive, MaintenanceMode } = require('../utils/maintenanceMode');
+
+/**
+ * 维护模式中间件
+ * 维护期间拦截所有非白名单请求，返回 503 状态码
+ */
+function maintenanceMiddleware(req, res, next) {
+  if (!isMaintenanceModeActive()) {
+    return next();
+  }
+
+  const isAllowed = MaintenanceMode.allowedRoutes.some((route) =>
+    req.path.startsWith(route)
+  );
+
+  if (isAllowed) {
+    return next();
+  }
+
+  return res.status(503).json({
+    success: false,
+    message: '系统正在维护中，请稍后再试',
+    maintenance: {
+      active: true,
+      reason: MaintenanceMode.reason,
+      startTime: MaintenanceMode.startTime,
+    },
+  });
+}
+
+module.exports = { maintenanceMiddleware };