The GRO-609 paymentStats useEffect fetches /api/invoices/stats/summary
on every render. Without a mock, the response {} (from the generic // Appointments,
clients, ... fallback) doesn't contain revenueThisMonth, causing the page
to fail rendering before AdminLayout ever mounts. Other admin pages don't
have this problem because they don't make unconditional side-effect fetches.
E2E tests mock all /api/** calls, so the new endpoint needs its own mock.
cc @cpfarhood
Test User
10ad5e7b04