Add E2E tests for internationalization across multiple pages

- Implemented navigation.spec.ts to test language switching and translation of navigation elements.
- Created sessions-page.spec.ts to verify translations on the sessions page, including headers, status badges, and date formatting.
- Developed settings-page.spec.ts to ensure settings page content is translated and persists across sessions.
- Added skills-page.spec.ts to validate translations for skill categories, action buttons, and empty states.

ccw/frontend/src/lib/query-client.ts

@@ -0,0 +1,30 @@
+// ========================================
+// Query Client Configuration
+// ========================================
+// TanStack Query client configuration for React
+
+import { QueryClient } from '@tanstack/react-query';
+
+/**
+ * Query client instance with default configuration
+ */
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      // Time in milliseconds that data remains fresh
+      staleTime: 1000 * 60 * 5, // 5 minutes
+      // Time in milliseconds that unused data is cached
+      gcTime: 1000 * 60 * 10, // 10 minutes
+      // Number of times to retry failed queries
+      retry: 1,
+      // Disable refetch on window focus for better UX
+      refetchOnWindowFocus: false,
+    },
+    mutations: {
+      // Number of times to retry failed mutations
+      retry: 1,
+    },
+  },
+});
+
+export default queryClient;