fix(sign_up): created paintz not linked after signing up

lib/modules/auth/data/data_sources/firebase_auth_remote_data_source.dart

@@ -70,17 +70,11 @@ class FirebaseAuthRemoteDataSource extends AuthRemoteDataSource {
     required final String password,
     final String? displayName,
   }) async {
-    late final UserCredential response;
-    response = await _firebaseAuth.createUserWithEmailAndPassword(
-      email: identifier,
-      password: password,
-    );
-
     final user = _firebaseAuth.currentUser;
     // link the anonymous user with a newly-created firebase user
-    if (response.credential != null) {
-      await user?.linkWithCredential(response.credential!);
-    }
+    final emailCredential =
+        EmailAuthProvider.credential(email: identifier, password: password);
+    final response = await user?.linkWithCredential(emailCredential);
 
     // only update the display name if one was supplied or it's different from
     // the current display name
@@ -89,7 +83,7 @@ class FirebaseAuthRemoteDataSource extends AuthRemoteDataSource {
       await updateUserDisplayName(displayName);
     }
 
-    return response.toModel();
+    return response!.toModel();
   }
 
   /// Sign out a user