feat(PingServices): add caching functionality for ping service results and enhance settings modal for cache duration configuration

frontend/src/components/SettingsModal.jsx

@@ -26,6 +26,7 @@ export default function SettingsModal({ open, onClose }) {
   const [pingServicesSource, setPingServicesSource] = useState('web');
   const [pingServicesServerId, setPingServicesServerId] = useState('');
   const [pingServicesGatewayIp, setPingServicesGatewayIp] = useState('');
+  const [pingServicesCacheSeconds, setPingServicesCacheSeconds] = useState('');
   const [serversList, setServersList] = useState([]);
 
   const routerServersForPing = useMemo(() => {
@@ -58,6 +59,7 @@ export default function SettingsModal({ open, onClose }) {
         setPingServicesSource(String(data?.pingServicesSource || 'web').toLowerCase() === 'router' ? 'router' : 'web');
         setPingServicesServerId(String(data?.pingServicesServerId || '').trim());
         setPingServicesGatewayIp(String(data?.pingServicesGatewayIp || '').trim());
+        setPingServicesCacheSeconds(data?.pingServicesCacheSeconds != null ? String(data.pingServicesCacheSeconds) : '');
         const e = settingsRes?.headers?.etag || settingsRes?.headers?.ETag || '';
         setEtag(e ? String(e) : '');
         setServersList(Array.isArray(serversRes?.data) ? serversRes.data : []);
@@ -126,6 +128,7 @@ export default function SettingsModal({ open, onClose }) {
         pingServicesSource: pingServicesSource === 'router' ? 'router' : 'web',
         pingServicesServerId: String(pingServicesServerId || '').trim(),
         pingServicesGatewayIp: String(pingServicesGatewayIp || '').trim(),
+        pingServicesCacheSeconds: Math.max(0, parseInt(pingServicesCacheSeconds, 10) || 0),
       };
       const payload = { 
         settings: mergedSettings, 
@@ -265,6 +268,19 @@ export default function SettingsModal({ open, onClose }) {
                   «Веб» — задержка до 8.8.8.8, 1.1.1.1 и др. с сервера. «Роутер» — пинг через выбранный MikroTik (jumphost).
                 </div>
               </div>
+              <div className="mb-2">
+                <FormField
+                  label="Время кеширования пингов (сек)"
+                  name="pingServicesCacheSeconds"
+                  type="number"
+                  value={pingServicesCacheSeconds}
+                  onChange={setPingServicesCacheSeconds}
+                  placeholder="0"
+                  helpText="0 — без кеша. Результаты пинга до Google, Cloudflare и др. будут кешироваться на указанное число секунд."
+                  disabled={loading || saving}
+                  min={0}
+                />
+              </div>
               {pingServicesSource === 'router' && (
                 <div className="row g-2">
                   <div className="col-md-6">