Hide "Email Commands" in user menu when no inbound mail configured
Summary:
Only show "Email Commands" in the top bar user menu (when being in an application) when inbound mail is configured (means: when `metamta.reply-handler-domain` is set) in the Phorge instance.
As a side effect, your local Phorge admin may receive less mail every day from frustrated users desperately asking to improve the server config and can reallocate time on adding more Cat Facts.
Closes T16180
Test Plan:
* Do not have http://phorge.localhost/config/edit/metamta.reply-handler-domain/ configured
* Go to http://phorge.localhost/differential/ or http://phorge.localhost/pholio/ and open the user menu in the top bar
* Do not see an entry "Email Commands" anymore
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T16180
Differential Revision: https://we.phorge.it/D26201