fix: power control 502 error and add instant refresh

- Power operations use /api2/extjs endpoint (not /api2/json)
- Remove unprivileged parameter that causes 400 validation error
- Refetch VM/LXC/node/status after successful power action via SWR mutate

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/components/Dashboard.js

@@ -1,7 +1,7 @@
 'use client';
 
 import { useState } from 'react';
-import useSWR from 'swr';
+import useSWR, { mutate } from 'swr';
 import NodeList from './NodeList';
 import VMList from './VMList';
 import LXCList from './LXCList';
@@ -45,6 +45,11 @@ export default function Dashboard() {
     setPowerActionStatus({ text: `${action.charAt(0).toUpperCase() + action.slice(1)}ing ${type === 'qemu' ? 'VM' : 'LXC'} ${vmid}...`, type: 'pending' });
     try {
       await axios.post('/api/power', { node, vmid, type, action });
+      // Immediately refetch all data instead of waiting for polling interval
+      await mutate('/api/nodes');
+      await mutate('/api/vms');
+      await mutate('/api/lxc');
+      await mutate('/api/status');
       setPowerActionStatus({ text: `${action.charAt(0).toUpperCase() + action.slice(1)} successful`, type: 'success' });
     } catch (err) {
       setPowerActionStatus({ text: err.message || `${action.charAt(0).toUpperCase() + action.slice(1)} failed`, type: 'error' });