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/app/(dashboard)/layout.tsx

@@ -3,6 +3,7 @@
 import Link from 'next/link';
 import { usePathname } from 'next/navigation';
 import { Button } from '@/components/ui/button';
+import { useTheme } from '@/components/providers/theme-provider';
 import { useAuthStore } from '@/lib/auth-store';
 import { cn } from '@/lib/utils';
 
@@ -19,6 +20,7 @@ const navItems = [
 export default function DashboardLayout({ children }: { children: React.ReactNode }) {
   const pathname = usePathname();
   const { user, logout } = useAuthStore();
+  const { theme, toggleTheme } = useTheme();
 
   return (
     <div className="min-h-screen bg-background">
@@ -53,6 +55,23 @@ export default function DashboardLayout({ children }: { children: React.ReactNod
                 {user.fullName}
               </span>
             )}
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={toggleTheme}
+              aria-label={theme === 'light' ? 'Chuyển sang chế độ tối' : 'Chuyển sang chế độ sáng'}
+              className="h-9 w-9 p-0"
+            >
+              {theme === 'light' ? (
+                <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z" />
+                </svg>
+              ) : (
+                <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 3v1m0 16v1m9-9h-1M4 12H3m15.364 6.364l-.707-.707M6.343 6.343l-.707-.707m12.728 0l-.707.707M6.343 17.657l-.707.707M16 12a4 4 0 11-8 0 4 4 0 018 0z" />
+                </svg>
+              )}
+            </Button>
             <Button variant="ghost" size="sm" onClick={() => logout()}>
               Đăng xuất
             </Button>