added back nav useeffect to login

Author: AnujaKalahara99

Frontend/src/components/login.tsx

@@ -1,5 +1,5 @@
 import { supabase } from "../database/superbase";
-import { useState } from "react";
+import { useEffect, useState } from "react";
 import { useNavigate } from "react-router";
 import { useTheme } from "../Contexts/ThemeProvider";
 import { AlertCircle, Sun, Moon, Code } from "lucide-react";
@@ -32,6 +32,16 @@ function Login() {
   const [error, setError] = useState<string | null>(null);
   const [loading, setLoading] = useState(false);
 
+  // Redirect if session exists
+  useEffect(() => {
+    const checkSession = async () => {
+      const {
+        data: { session },
+      } = await supabase.auth.getSession();
+      if (session) navigate("/dashboard");
+    };
+    checkSession();
+  }, [navigate]);
 
   const signInWithGoogle = async () => {
     setError(null);