fix: remove unused imports in test files

Remove unused useClients import and mockPaymentDetailQuery variable
to fix lint errors.

Author: bjcoombs

frontend/src/features/parties/pages/tabs/associations-tab.test.tsx

@@ -28,7 +28,7 @@ vi.mock('@/hooks/use-tenant-context', () => ({
   useClearTenant: () => vi.fn(),
 }))
 
-import { useClients, useApiClients } from '@/api/context'
+import { useApiClients } from '@/api/context'
 import { AssociationsTab } from './associations-tab'
 
 function makeQueryClient() {

frontend/src/features/payments/pages/payment-detail.test.tsx

@@ -7,8 +7,6 @@ import { TooltipProvider } from '@/components/ui/tooltip'
 import { AuthProvider } from '@/contexts/auth-context'
 import { TenantProvider } from '@/contexts/tenant-context'
 // Mock the payment detail hook
-const mockPaymentDetailQuery = vi.fn()
-
 vi.mock('../hooks', () => ({
   usePaymentDetail: vi.fn(() => ({
     data: null,