auth with handler

app/AuthHandler.tsx

@@ -0,0 +1,45 @@
+import { useRouter, useSegments } from "expo-router";
+import { onAuthStateChanged } from "firebase/auth";
+import { doc, getDoc } from "firebase/firestore";
+import { useEffect } from "react";
+import { auth, db } from "../firebase_config";
+import { useUser } from "./ContextUser";
+
+export function useAuthHandler() {
+  const router = useRouter();
+  const segments = useSegments();
+  const { setUser, setRole } = useUser();
+
+  useEffect(() => {
+    const unsubscribe = onAuthStateChanged(auth, async (currentUser) => {
+      if (!currentUser) {
+        setUser(null);
+        setRole(null);
+        router.replace("/login/login");
+        return;
+      }
+
+      const userDocRef = doc(db, "user", currentUser.uid);
+      const userDoc = await getDoc(userDocRef);
+
+      if (!userDoc.exists()) {
+        setUser(null);
+        setRole(null);
+        router.replace("/login/login");
+        return;
+      }
+
+      const { role } = userDoc.data();
+      setUser(currentUser);
+      setRole(role);
+      
+      // Only redirect if we're on login page
+      const inAuthGroup = segments[0] === 'login';
+      if (inAuthGroup) {
+        router.replace("/(tabs)/home");
+      }
+    });
+    
+    return unsubscribe;
+  }, []);
+}