Change default "contact form" email address from brigade-info@ CfA email

We just got an email from someone who used [the "Contact Us" page](https://codeforcroatia.org/contact) on the codeforcroatia.org instance of Laddr. It happened to be spam, but that led me to investigate how we got it, and I noticed that the default email address for the contact form is brigade-info@. This strikes me as almost certainly not the place you want to send users, since they're not going to get a response from the right people.

Not sure what the right fix is -- consider changing it to a value that must be configured? Or disable the page if the value is not provided?

Start at the Contact Us page configuration and trace how its recipient email is selected. Determine whether the default address can be safely changed, made required, or used to disable the page; done means submissions no longer go to an unintended default recipient.

Scritto dal modello di indicizzazione a partire dal testo della issue.