feat(web): add React Query, dark mode toggle, and error retry UX

- Install @tanstack/react-query with exponential backoff retry config
- Create QueryClientProvider and custom hooks for listings, analytics,
  payments, and subscription API calls
- Migrate 5 dashboard pages from useState/useEffect to React Query hooks
- Add dark mode CSS variables and ThemeProvider with localStorage persistence
- Add theme toggle button in dashboard header (sun/moon icon)
- Enhance error boundaries with auto-retry, retry count, and loading state

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/lib/hooks/use-payments.ts

@@ -0,0 +1,28 @@
+import { useQuery } from '@tanstack/react-query';
+import { paymentApi } from '@/lib/payment-api';
+
+export const paymentKeys = {
+  all: ['payments'] as const,
+  transactions: (params: { status?: string; limit?: number; offset?: number }) =>
+    ['payments', 'transactions', params] as const,
+  status: (id: string) => ['payments', 'status', id] as const,
+};
+
+export function useTransactions(params: {
+  status?: string;
+  limit?: number;
+  offset?: number;
+} = {}) {
+  return useQuery({
+    queryKey: paymentKeys.transactions(params),
+    queryFn: () => paymentApi.getTransactions(params),
+  });
+}
+
+export function usePaymentStatus(id: string) {
+  return useQuery({
+    queryKey: paymentKeys.status(id),
+    queryFn: () => paymentApi.getPaymentStatus(id),
+    enabled: !!id,
+  });
+}