Update application theme to use a lighter background

Adjusted CSS variables in `index.css` to change the primary background, foreground, card, popover, muted, accent, border, and input colors. Also removed the 'dark' class from the main div in `App.tsx` to revert to a light theme.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/gEOddVG

client/src/App.tsx

@@ -85,7 +85,7 @@ function App() {
   return (
     <QueryClientProvider client={queryClient}>
       <TooltipProvider>
-        <div className="dark">
+        <div>
           <Toaster />
           <Router />
         </div>