feat(UptimeMonitor): add uptime check endpoint and frontend settings for monitoring server availability

backend/server.js

@@ -470,6 +470,9 @@ app.post('/api/mikrotik/run-script', mikrotikConfigRoutes.runScript);
 app.get('/api/mikrotik/address-lists', mikrotikConfigRoutes.getAddressLists);
 app.post('/api/mikrotik/address-lists/apply-summary', writeLimiter, mikrotikConfigRoutes.applyAddressListSummary);
 
+// === UPTIME MONITOR (проверка доступности: http / internal-ping / external-ping из настроек) ===
+app.post('/api/uptime/check', writeLimiter, mikrotikConfigRoutes.uptimeCheck);
+
 // === TRAFFIC STATS (MikroTik interfaces by jumphost) ===
 app.get('/api/traffic/interface-stats', trafficRoutes.getInterfaceStats);