I think the issue is an easy fix per this documentation
Connection Strings and Configuration Files - ADO.NET | Microsoft Learn[
^]
The difference being that the inner part should be "connectionString" instead of "connectionStrings"
Try:
<connectionStrings>
<add name="constr1"
connectionString ="Data Source=DESKTOP-624ATVA\Mjavadabedi;Initial Catalog=sign in data;Integrated Security=true"
providerName="System.Data.SqlClient"/>
</connectionStrings>
Finally, if you're using SQL Server 2022, you may also need to add ";Encrypt=False" to the end of your connection string. At least helps with my local debugging.