fix: react-doctor → 64/100 (Bugs 122, Perf 286, A11y 613, Maint 436)

- CartContext: lazy initializers replace mount-only useEffect
  hydration; remove 8 no-initialize-state warnings
- Toast/AdminSearchInput: React 19 useContext/use + drop
  forwardRef (3 no-react19-deprecated-apis)
- ProductFormModal: lazy initializers + useSyncExternalStore
  for mount; parent adds key=editingProduct.id
- InstallPrompt: useReducer for prompt state (no-cascading-set-state)
- QRScanModal: ref-based latest-callback pattern replaces
  useEffectEvent deps mistake
- OnboardingFlow: functional setState (rerender-functional-setstate)
- UsersPage/StopsCalendar/FeaturesAndStats: lazy initializers
  (rerender-lazy-state-init)
- FAQClientPage: server-side brand settings fetch via getBrandSettingsPublic
  in layout; remove supabase import
- LandingPageWrapper: href='#' → href='#top' (anchor-is-valid)
- TuxedoVideoHero: replace animate-bounce with ease-out-expo
  (no-inline-bounce-easing)
- ProductTableClient: useCallback for handleDeleted
  (jsx-no-new-function-as-prop)
- excel-parser: pre-compile delimiter regexes (js-hoist-regexp)
- water-log/settings: Promise.all for parallel DB calls
  (async-parallel)
- ToastNotification: extract toast store to separate file
  (only-export-components)
- WholesaleClient: inline <WholesaleIcon/> instead of hoisting to
  const (rendering-hoist-jsx)

src/app/admin/settings/integrations/IntegrationsClientPage.tsx

@@ -119,14 +119,11 @@ function IntegrationCard({
   const [saving, setSaving] = useState(false);
   const [saved, setSaved] = useState(false);
   const [error, setError] = useState<string | null>(null);
-  const [dirty, setDirty] = useState(false);
 
-  // Track dirty state
-  useEffect(() => {
-    const hasValues = Object.values(credentials).some((v) => v.trim().length > 0);
-    // eslint-disable-next-line react-hooks/set-state-in-effect
-    setDirty(hasValues && JSON.stringify(initialCredentials) !== JSON.stringify(credentials));
-  }, [credentials, initialCredentials]);
+  // Derived from `credentials` + `initialCredentials` during render so we
+  // don't pay for an extra commit and stale-frame window.
+  const hasValues = Object.values(credentials).some((v) => v.trim().length > 0);
+  const dirty = hasValues && JSON.stringify(initialCredentials) !== JSON.stringify(credentials);
 
   async function handleTest() {
     setTestResult(null);