Add login check to mailbox manage module

Summary

See title

Steps to reproduce

• logout
• visit: https://beta.foodsharing.de/?page=mailbox&a=manage

What is the current bug behavior?

You see an empty site maybe executing something

What is the expected correct behavior?

• redirect to login if not logged in
• redirect to dashboard if you don't have permission to enter this site

Relevant error messages and/or screenshots

Possible fixes

• redirect to login if may() is false
• redirect to dashboard if $this->mailboxPermissions->mayManageMailboxes() is false