Add check that the Azure Dev and Prod connection string secrets are not the same

There is a potential that due to wrong copy and paste they might both deploy to the same blob.

Start by locating where the Azure Dev and Prod connection string secrets are read and where deployment validation occurs. Add a check that rejects identical values before deployment, and verify that different connection strings continue to deploy normally while matching values are blocked.

Written by the indexing model from the issue text.