perf: add Zustand selectors to prevent cascading re-renders

Replace all bare useAuthStore(), useBlockingStore(), and
useSuccessNotification() calls with individual field selectors.
This prevents components from re-rendering when unrelated store
fields change.

- 21 useAuthStore usages across 20 files: individual selectors
  for 1-2 fields, useShallow for 3+ fields
- 5 useBlockingStore usages: individual selectors
- 2 useSuccessNotification usages: individual selectors

src/components/WebSocketNotifications.tsx

@@ -18,9 +18,9 @@ export default function WebSocketNotifications() {
   const navigate = useNavigate();
   const queryClient = useQueryClient();
   const { showToast } = useToast();
-  const { refreshUser } = useAuthStore();
+  const refreshUser = useAuthStore((state) => state.refreshUser);
   const { formatAmount, currencySymbol } = useCurrency();
-  const { show: showSuccessModal } = useSuccessNotification();
+  const showSuccessModal = useSuccessNotification((state) => state.show);
 
   const handleMessage = useCallback(
     (message: WSMessage) => {