feat: move accounts pages to features/accounts module (#1396)

Relocates all files from frontend/src/pages/accounts/ to
frontend/src/features/accounts/pages/ and updates all imports.

- Update features/accounts/index.ts to export AccountsPage and AccountDetailPage
- Update App.tsx to import from @/features/accounts barrel
- Update payment-form-utils.ts cross-reference to use @/features/accounts/pages/account-form-utils

Co-authored-by: Ben Coombs <bjcoombs@users.noreply.github.com>

Author: bjcoombs

frontend/src/App.tsx

@@ -13,8 +13,7 @@ import { AppShell } from '@/components/layout/app-shell'
 import { TooltipProvider } from '@/components/ui/tooltip'
 import { TenantsPage } from '@/pages/tenants/index'
 import { TenantDetailPage } from '@/pages/tenants/[tenantId]'
-import { AccountsPage } from '@/pages/accounts'
-import { AccountDetailPage } from '@/pages/accounts/[accountId]'
+import { AccountsPage, AccountDetailPage } from '@/features/accounts'
 import { PaymentsPage } from '@/pages/payments'
 import { PaymentDetailPage } from '@/pages/payments/payment-detail'
 import { PartiesPage } from '@/pages/parties'

frontend/src/features/accounts/index.ts

@@ -1 +1,3 @@
 // Public API for accounts module
+export { AccountsPage } from './pages/index'
+export { AccountDetailPage } from './pages/[accountId]'