refactor(snowball): migrate SnowballPage to React Query (R5.5)

useSnowball + useSnowballSettings + useSnowballActivePlan + useSnowballPlans
(+ shared useCategories). The settings-derived form fields (extra payment,
ramsey mode, ready flags) are seeded via a settings-synced effect; the many
optimistic list/plan edits route through queryClient.setQueryData wrappers;
load() is an invalidate wrapper. The debounced live-projection stays a client
computation (not page data). Removed the now-dead loadPlans (hooks auto-fetch).

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

client/hooks/useQueries.js

@@ -110,6 +110,30 @@ export function useSummary(year, month) {
   });
 }
 
+export function useSnowball() {
+  return useQuery({ queryKey: ['snowball'], queryFn: () => api.snowball(), staleTime: 1000 * 60 * 2 });
+}
+
+export function useSnowballSettings() {
+  return useQuery({ queryKey: ['snowball-settings'], queryFn: () => api.snowballSettings(), staleTime: 1000 * 60 * 2 });
+}
+
+export function useSnowballActivePlan() {
+  return useQuery({
+    queryKey: ['snowball-active-plan'],
+    queryFn: () => api.snowballActivePlan().catch(() => null),
+    staleTime: 1000 * 60 * 2,
+  });
+}
+
+export function useSnowballPlans() {
+  return useQuery({
+    queryKey: ['snowball-plans'],
+    queryFn: () => api.snowballPlans().then(d => d?.plans ?? []).catch(() => []),
+    staleTime: 1000 * 60 * 2,
+  });
+}
+
 export function useSubscriptions() {
   return useQuery({
     queryKey: ['subscriptions'],

client/pages/SnowballPage.jsx

@@ -1,4 +1,8 @@
 import { useCallback, useEffect, useRef, useState } from 'react';
+import { useQueryClient } from '@tanstack/react-query';
+import {
+  useSnowball, useSnowballSettings, useSnowballActivePlan, useSnowballPlans, useCategories,
+} from '@/hooks/useQueries';
 import { ArrowDown, ArrowUp, GripVertical, TrendingDown, Zap, Save, CalendarCheck, AlertTriangle, PenLine, EyeOff, CheckCircle2, Circle, AlertCircle, RefreshCw } from 'lucide-react';
 import { toast } from 'sonner';
 import { api } from '@/api';
@@ -266,10 +270,22 @@ function ReadinessStrip({ items, readyCount, totalCount, allReady, onToggle, dis
 
 // ── Page ──────────────────────────────────────────────────────────────────────
 export default function SnowballPage() {
-  const [bills,      setBills]      = useState([]);
-  const [categories, setCategories] = useState([]);
-  const [loading,    setLoading]    = useState(true);
-  const [loadError,  setLoadError]  = useState(null);
+  const queryClient = useQueryClient();
+  const { data: bills = [], isPending: billsPending, error: snowballError } = useSnowball();
+  const { data: categories = [] } = useCategories();
+  const { data: settings } = useSnowballSettings();
+  const { data: activePlan = null } = useSnowballActivePlan();
+  const { data: allPlans = [] } = useSnowballPlans();
+  const loading = billsPending;
+  const loadError = snowballError ? (snowballError.message || 'Failed to load snowball data') : null;
+  // Optimistic list/plan edits write through the query cache so existing call
+  // sites (setBills(prev => …), setActivePlan(…), setAllPlans(prev => …)) work.
+  const setBills = useCallback((u) => queryClient.setQueryData(['snowball'],
+    prev => (typeof u === 'function' ? u(prev || []) : u)), [queryClient]);
+  const setActivePlan = useCallback((u) => queryClient.setQueryData(['snowball-active-plan'],
+    prev => (typeof u === 'function' ? u(prev ?? null) : u)), [queryClient]);
+  const setAllPlans = useCallback((u) => queryClient.setQueryData(['snowball-plans'],
+    prev => (typeof u === 'function' ? u(prev || []) : u)), [queryClient]);
   const [saving,     setSaving]     = useState(false);
   const [dirty,      setDirty]      = useState(false);
   const [editBill,   setEditBill]   = useState(null);
@@ -288,8 +304,6 @@ export default function SnowballPage() {
 
   const [editingBalance, setEditingBalance] = useState({ billId: null, value: '' });
 
-  const [activePlan,        setActivePlan]        = useState(null);
-  const [allPlans,          setAllPlans]          = useState([]);
   const [startingPlan,      setStartingPlan]      = useState(false);
   const [readinessWarnOpen, setReadinessWarnOpen] = useState(false);
   const [draggingId,        setDraggingId]        = useState(null);
@@ -311,33 +325,27 @@ export default function SnowballPage() {
     } finally { setProjectionLoading(false); }
   }, []);
 
-  const load = useCallback(async () => {
-    setLoading(true);
-    setLoadError(null);
-    try {
-      const [billsArr, catsArr, settings] = await Promise.all([
-        api.snowball(), api.categories(), api.snowballSettings(),
-      ]);
-      setCategories(catsArr);
-      setBills(billsArr);
-      setDirty(false);
-      const ep = settings.extra_payment > 0 ? String(settings.extra_payment) : '';
-      setRamseyMode(settings.ramsey_mode !== false);
-      setReadyCurrentOnBills(!!settings.ready_current_on_bills);
-      setReadyEmergencyFund(!!settings.ready_emergency_fund);
-      setExtraPayment(ep);
-      extraPaymentRef.current = ep;
-    } catch (err) {
-      setLoadError(err.message || 'Failed to load snowball data');
-    } finally { setLoading(false); }
-  }, []);
+  const load = useCallback(() => Promise.all([
+    queryClient.invalidateQueries({ queryKey: ['snowball'] }),
+    queryClient.invalidateQueries({ queryKey: ['categories'] }),
+    queryClient.invalidateQueries({ queryKey: ['snowball-settings'] }),
+  ]), [queryClient]);
 
-  const loadPlans = useCallback(() => {
-    api.snowballActivePlan().then(p => setActivePlan(p)).catch(() => setActivePlan(null));
-    api.snowballPlans().then(d => setAllPlans(d?.plans ?? [])).catch(err => console.error('[SnowballPage] failed to load plan history', err));
-  }, []);
+  // Seed the editable settings form (extra payment, ramsey mode, ready flags)
+  // from the loaded settings whenever they change — this is what `load` did inline.
+  useEffect(() => {
+    if (!settings) return;
+    setDirty(false);
+    const ep = settings.extra_payment > 0 ? String(settings.extra_payment) : '';
+    setRamseyMode(settings.ramsey_mode !== false);
+    setReadyCurrentOnBills(!!settings.ready_current_on_bills);
+    setReadyEmergencyFund(!!settings.ready_emergency_fund);
+    setExtraPayment(ep);
+    extraPaymentRef.current = ep;
+  }, [settings]);
 
-  useEffect(() => { Promise.all([load(), loadProjection()]); loadPlans(); }, [load, loadProjection, loadPlans]);
+  // The live projection stays a debounced client computation (not page data).
+  useEffect(() => { loadProjection(); }, [loadProjection]);
 
   // ── auto-arrange ──────────────────────────────────────────────────────────
   const handleAutoArrange = () => {