refactor(analytics): migrate AnalyticsPage to React Query (R5.1)

Replaced the manual useState(data/loading/error) + load useCallback + useEffect
(and the R3 request-seq guard) with a useAnalyticsSummary(params) query hook.
React Query now handles caching, dedup, cancellation, and out-of-order responses
via the params-encoded key; keepPreviousData keeps the last result visible while
a new month/filter loads. Refresh -> refetch; the redundant page-load error toast
is dropped in favor of the existing inline error state.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/hooks/useQueries.js

@@ -1,4 +1,4 @@
-import { useQuery, useQueryClient } from '@tanstack/react-query';
+import { useQuery, useQueryClient, keepPreviousData } from '@tanstack/react-query';
 import { useCallback } from 'react';
 import { api } from '@/api';
 
@@ -67,3 +67,17 @@ export function useInvalidateTrackerData() {
     }
   }, [queryClient]);
 }
+
+// ── Page data (migrated off manual useEffect + load()) ───────────────────────
+// The queryKey encodes the params, so React Query handles caching, request
+// dedup, cancellation, and out-of-order responses — no manual sequence guards.
+// keepPreviousData keeps the last result visible while a new month/filter loads.
+
+export function useAnalyticsSummary(params) {
+  return useQuery({
+    queryKey: ['analytics-summary', params],
+    queryFn: () => api.analyticsSummary(params),
+    staleTime: 1000 * 60 * 2,
+    placeholderData: keepPreviousData,
+  });
+}

client/pages/AnalyticsPage.jsx

@@ -1,8 +1,7 @@
-import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import React, { useMemo, useState } from 'react';
 import { formatUSD, formatUSDWhole } from '@/lib/money';
 import { Printer, RefreshCw, RotateCcw } from 'lucide-react';
-import { toast } from 'sonner';
+import { useAnalyticsSummary } from '@/hooks/useQueries';
-import { api } from '@/api';
 import { Button } from '@/components/ui/button';
 import { Skeleton } from '@/components/ui/Skeleton';
 import { cn } from '@/lib/utils';
@@ -490,9 +489,6 @@ export default function AnalyticsPage() {
   const [includeInactive, setIncludeInactive] = useState(false);
   const [includeSkipped, setIncludeSkipped] = useState(true);
   const [trendMode, setTrendMode] = useState('line');
-  const [data, setData] = useState(null);
-  const [loading, setLoading] = useState(true);
-  const [error, setError] = useState('');
   const [visible, setVisible] = useState({
     monthlyTrend: true,
     expectedActual: true,
@@ -512,26 +508,10 @@ export default function AnalyticsPage() {
     include_skipped: includeSkipped,
   }), [billId, categoryId, includeInactive, includeSkipped, month, months, year]);
 
-  const requestSeq = useRef(0);
+  // React Query handles caching, dedup, cancellation, and out-of-order responses.
-  const load = useCallback(async () => {
+  const { data, isPending, isFetching, error: queryError, refetch } = useAnalyticsSummary(params);
-    // Ignore out-of-order responses: only the newest request updates state, so a
+  const loading = isPending;
-    // slow response for old params can't overwrite fresh data (or setState after
+  const error = queryError ? (queryError.message || 'Failed to load analytics.') : '';
-    // unmount). Same guard the Bank ledger uses.
-    const seq = ++requestSeq.current;
-    setLoading(true);
-    setError('');
-    try {
-      const result = await api.analyticsSummary(params);
-      if (seq === requestSeq.current) setData(result);
-    } catch (err) {
-      if (seq === requestSeq.current) setError(err.message || 'Failed to load analytics.');
-      toast.error(err.message || 'Failed to load analytics.');
-    } finally {
-      if (seq === requestSeq.current) setLoading(false);
-    }
-  }, [params]);
-
-  useEffect(() => { load(); }, [load]);
 
   const forecastRows = useMemo(
     () => linearForecast(data?.monthly_spending || [], forecastHorizon),
@@ -579,8 +559,8 @@ export default function AnalyticsPage() {
           </p>
         </div>
         <div className="analytics-actions flex flex-wrap gap-2">
-          <Button variant="outline" size="sm" onClick={load} disabled={loading} className="flex-1 sm:flex-none">
+          <Button variant="outline" size="sm" onClick={() => refetch()} disabled={isFetching} className="flex-1 sm:flex-none">
-            <RefreshCw className={cn('h-3.5 w-3.5', loading && 'animate-spin')} />
+            <RefreshCw className={cn('h-3.5 w-3.5', isFetching && 'animate-spin')} />
             Refresh
           </Button>
           <Button variant="outline" size="sm" onClick={() => window.print()} className="flex-1 sm:flex-none">