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/components/providers/query-provider.tsx

@@ -0,0 +1,9 @@
+'use client';
+
+import { QueryClientProvider } from '@tanstack/react-query';
+import { getQueryClient } from '@/lib/query-client';
+
+export function QueryProvider({ children }: { children: React.ReactNode }) {
+  const queryClient = getQueryClient();
+  return <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>;
+}