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>;
+}

apps/web/components/providers/theme-provider.tsx

@@ -0,0 +1,51 @@
+'use client';
+
+import { createContext, useCallback, useContext, useEffect, useState } from 'react';
+
+type Theme = 'light' | 'dark';
+
+interface ThemeContextValue {
+  theme: Theme;
+  toggleTheme: () => void;
+}
+
+const ThemeContext = createContext<ThemeContextValue>({
+  theme: 'light',
+  toggleTheme: () => {},
+});
+
+export function useTheme() {
+  return useContext(ThemeContext);
+}
+
+const STORAGE_KEY = 'goodgo-theme';
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const [theme, setTheme] = useState<Theme>('light');
+
+  useEffect(() => {
+    const stored = localStorage.getItem(STORAGE_KEY) as Theme | null;
+    if (stored === 'dark' || stored === 'light') {
+      setTheme(stored);
+      document.documentElement.classList.toggle('dark', stored === 'dark');
+    } else if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+      setTheme('dark');
+      document.documentElement.classList.add('dark');
+    }
+  }, []);
+
+  const toggleTheme = useCallback(() => {
+    setTheme((prev) => {
+      const next = prev === 'light' ? 'dark' : 'light';
+      localStorage.setItem(STORAGE_KEY, next);
+      document.documentElement.classList.toggle('dark', next === 'dark');
+      return next;
+    });
+  }, []);
+
+  return (
+    <ThemeContext.Provider value={{ theme, toggleTheme }}>
+      {children}
+    </ThemeContext.Provider>
+  );
+}