Fix K-profiles backup status showing incorrect printer connection count

The GitHub backup settings page was showing "1/2 connected" even when
both printers were connected. This happened because the code read
printer status from the React Query cache, which is only populated by
WebSocket messages received on other pages.

Changed to use useQueries to fetch printer status directly from the API
(/api/v1/printers/{id}/status) instead of relying on cached WebSocket
data. Results are cached for 10s and refreshed every 30s.

frontend/src/components/GitHubBackupSettings.tsx

@@ -1,5 +1,5 @@
 import { useState, useEffect, useRef, useCallback } from 'react';
-import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { useQuery, useQueries, useMutation, useQueryClient } from '@tanstack/react-query';
 import {
   Github,
   Play,
@@ -27,7 +27,6 @@ import type {
   ScheduleType,
   CloudAuthStatus,
   Printer,
-  PrinterStatus,
 } from '../api/client';
 import { Card, CardContent, CardHeader } from './Card';
 import { Button } from './Button';
@@ -149,11 +148,20 @@ export function GitHubBackupSettings() {
     queryFn: api.getPrinters,
   });
 
-  // Get printer statuses from cache (populated by WebSocket on other pages)
-  const printerStatuses = printers?.map(p => {
-    const status = queryClient.getQueryData<PrinterStatus>(['printerStatus', p.id]);
-    return { printer: p, connected: status?.connected ?? false };
-  }) ?? [];
+  // Fetch printer statuses from API (not just cache) to get accurate connection status
+  const printerStatusQueries = useQueries({
+    queries: (printers ?? []).map(printer => ({
+      queryKey: ['printerStatus', printer.id],
+      queryFn: () => api.getPrinterStatus(printer.id),
+      staleTime: 10000, // Consider stale after 10s
+      refetchInterval: 30000, // Refresh every 30s
+    })),
+  });
+
+  const printerStatuses = (printers ?? []).map((printer, index) => ({
+    printer,
+    connected: printerStatusQueries[index]?.data?.connected ?? false,
+  }));
 
   const totalPrinters = printerStatuses.length;
   const connectedPrinters = printerStatuses.filter(p => p.connected).length;