feat(PingServices): implement history tracking for ping results and update API responses to include historical data

frontend/src/Dashboard.jsx

@@ -78,8 +78,6 @@ function MetricCard({ title, value, icon: Icon, color, description }) {
   );
 }
 
-const PING_HISTORY_MAX = 30;
-
 /** Обёртка для Sparkline по ширине контейнера */
 function PingSparklineWrap({ history, color }) {
   const wrapRef = useRef(null);
@@ -191,7 +189,6 @@ function Dashboard() {
   const [pingServices, setPingServices] = useState(null);
   const [pingServicesConfig, setPingServicesConfig] = useState([]);
   const [pingLoading, setPingLoading] = useState(true);
-  const [previousPingServices, setPreviousPingServices] = useState(null);
   const [pingHistory, setPingHistory] = useState(() => ({}));
   const [expandedPingId, setExpandedPingId] = useState(null);
 
@@ -308,26 +305,11 @@ function Dashboard() {
     setPingLoading(true);
     api.get('/ping-services', { params: forceRefresh ? { refresh: 1 } : {} })
       .then(({ data }) => {
-        const next = data && typeof data === 'object' ? data : null;
-        setPingServices((current) => {
-          if (current && typeof current === 'object' && Object.keys(current).length > 0) {
-            setPreviousPingServices(current);
-          }
-          return next;
-        });
-        if (next) {
-          setPingHistory((h) => {
-            const out = { ...h };
-            Object.keys(next).forEach((id) => {
-              const ms = next[id]?.ms;
-              if (typeof ms !== 'number') return;
-              const list = Array.isArray(out[id]) ? out[id] : [];
-              const nextList = [...list, ms].slice(-PING_HISTORY_MAX);
-              out[id] = nextList;
-            });
-            return out;
-          });
-        }
+        if (!data || typeof data !== 'object') return;
+        const byId = data.byId ?? data;
+        const history = data.history ?? {};
+        setPingServices(byId);
+        setPingHistory(typeof history === 'object' ? history : {});
       })
       .catch(() => setPingServices(null))
       .finally(() => setPingLoading(false));
@@ -391,7 +373,10 @@ function Dashboard() {
             <PingServiceCard
               config={config}
               ms={pingServices?.[config.id]?.ms ?? null}
-              previousMs={previousPingServices?.[config.id]?.ms ?? null}
+              previousMs={(() => {
+              const hist = pingHistory[config.id] || [];
+              return hist.length >= 2 ? hist[hist.length - 2] : null;
+            })()}
               history={pingHistory[config.id] || []}
               loading={pingLoading}
               isExpanded={expandedPingId === config.id}