refactor: clean up unused ThemeProvider code and CSS variables

apps/landing/src/app/_components/providers.tsx

@@ -3,21 +3,9 @@
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
 import type { ThemeProviderProps } from 'next-themes';
 import { ReactNode } from 'react';
-// import { ThemeProvider as NextThemesProvider } from 'next-themes';
 
 export function Providers({ children }: ThemeProviderProps) {
-  return (
-    <QueryProvider>
-      {/* <ThemeProvider
-        attribute="class"
-        defaultTheme="light"
-        enableSystem
-        disableTransitionOnChange
-      > */}
-      {children}
-      {/* </ThemeProvider> */}
-    </QueryProvider>
-  );
+  return <QueryProvider>{children}</QueryProvider>;
 }
 
 export const queryClient = new QueryClient();
@@ -27,7 +15,3 @@ function QueryProvider({ children }: { children: ReactNode }) {
     <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
   );
 }
-
-// function ThemeProvider({ children, ...props }: ThemeProviderProps) {
-//   return <NextThemesProvider {...props}>{children}</NextThemesProvider>;
-// }