fix: cart badge not updating after account creation due to stale closure

frontend/src/cart/CartContext.tsx

@@ -19,11 +19,18 @@ export function CartProvider({ children }: { children: React.ReactNode }) {
   const { customer } = useCustomerAuth();
 
   const refresh = useCallback(() => {
-    if (!customer) { setItems([]); return; }
+    fetchCart()
-    fetchCart().then(data => setItems(data.items)).catch(() => setItems([]));
+      .then(data => setItems(data.items))
-  }, [customer]);
+      .catch(() => setItems([]));
+  }, []);
 
-  useEffect(() => { refresh(); }, [refresh]);
+  useEffect(() => {
+    if (customer) {
+      refresh();
+    } else {
+      setItems([]);
+    }
+  }, [customer, refresh]);
 
   const itemIds = new Set(items.map(i => i.item_id));