fix: stabilize admin dashboard navigation

frontend/src/pages/Dashboard/Dashboard.tsx

@@ -90,6 +90,8 @@ const RESTART_GUIDE_LINES: Record<RestartAction, string[]> = {
   ],
 }
 
+let cachedDashboardStats: Stats | null = null
+
 function getRestartConfirmMessage(action: RestartAction): string {
   if (action === 'restart-database') {
     return '将重启 PostgreSQL 和 Redis，页面通常保持在线，但相关请求可能短暂波动。'
@@ -102,8 +104,8 @@ function getRestartConfirmMessage(action: RestartAction): string {
 
 function Dashboard() {
   const { token, clearAuth, user } = useAuthStore()
-  const [stats, setStats] = useState<Stats | null>(null)
-  const [loading, setLoading] = useState(true)
+  const [stats, setStats] = useState<Stats | null>(cachedDashboardStats)
+  const [loading, setLoading] = useState(cachedDashboardStats === null)
   const [wsConnected, setWsConnected] = useState(false)
   const [error, setError] = useState<string | null>(null)
   const [restartModalOpen, setRestartModalOpen] = useState(false)
@@ -122,7 +124,9 @@ function Dashboard() {
 
     const fetchStats = async () => {
       try {
-        setLoading(true)
+        if (!cachedDashboardStats) {
+          setLoading(true)
+        }
         const res = await fetch('/api/v1/dashboard/stats', {
           headers: { Authorization: `Bearer ${token}` },
         })
@@ -132,6 +136,7 @@ function Dashboard() {
           return
         }
         const data = await res.json()
+        cachedDashboardStats = data
         setStats(data)
         setError(null)
       } catch (err) {
@@ -164,7 +169,9 @@ function Dashboard() {
           try {
             const msg = JSON.parse(event.data)
             if (msg.type === 'data_frame' && msg.channel === 'dashboard') {
-              setStats(msg.payload?.stats as Stats)
+              const nextStats = msg.payload?.stats as Stats
+              cachedDashboardStats = nextStats
+              setStats(nextStats)
             }
           } catch (e) {
             console.error('Parse WS message error:', e)