Show personal foodsharing.network e-mail address somewhere (for oneself and other users)

Description

Currently it is hard for foodsharers to find their own @foodsharing.network e-mail address, as displayed on the fs-business card (https://foodsharing.de/?page=bcard).

Impact

foodsaver and above

Proposal

Put the internal email address

• on the profile page (so that for now only the foodsharer himself can see it. As this is related to #734, if only I can see my @, no data security matter is breached) and maybe also
• under the top menu-tab containing the letter-symbol.

Links / references

We have a "lost@foodsharing.network" that gets all mails that don't find any "postfach" - it is not really maintained - sometimes i look at it and it seems that users have trouble finding their own or e-mail addresses from others.