feat(ui): add modal functionality, leaderboard view

app/providers.tsx

@@ -3,12 +3,15 @@
 import { ExamProvider } from "@/context/ExamContext";
 import { TimerProvider } from "@/context/TimerContext";
 import { AuthProvider } from "@/context/AuthContext";
+import { ModalProvider } from "@/context/ModalContext";
 
 export function Providers({ children }: { children: React.ReactNode }) {
   return (
     <TimerProvider>
       <AuthProvider>
-        <ExamProvider>{children}</ExamProvider>
+        <ExamProvider>
+          <ModalProvider>{children}</ModalProvider>
+        </ExamProvider>
       </AuthProvider>
     </TimerProvider>
   );