fix: reduce WebSocket refresh interval to 10s for live MQTT data

- Client ping interval: 15s → 10s
- Server timeout fallback: 20s → 12s
- Ensures CPU/RAM values update promptly from MQTT store

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/routers/dashboard.py

@@ -91,7 +91,7 @@ async def ws_endpoint(ws: WebSocket) -> None:
         while True:
             # Wait for a client ping / keepalive; refresh on timeout too.
             try:
-                _msg = await asyncio.wait_for(ws.receive_text(), timeout=20.0)
+                _msg = await asyncio.wait_for(ws.receive_text(), timeout=12.0)
             except asyncio.TimeoutError:
                 pass
 

web/src/hooks/useWebSocket.ts

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 import type { DashboardData } from "../api";
 
 const WS_RECONNECT_MS = 5_000;
-const WS_PING_INTERVAL_MS = 15_000;
+const WS_PING_INTERVAL_MS = 10_000;
 
 export function useWebSocket() {
   const [data, setData] = useState<DashboardData | null>(null);