Put our link to all mails and sync the formatting

src/mail_templates/user_event.ejs

@@ -1,15 +1,14 @@
 <%if (format === 'text') { %>
 
-Dear Admin,
+Dear Cloudron Admin,
 
 User <%= user.username || user.alternateEmail || user.email %> <%= event %> in the Cloudron at <%= fqdn %>.
 
 You are receiving this email because you are an Admin of the Cloudron at <%= fqdn %>.
 
-Thank you,
-User Manager
+
+Powered by https://cloudron.io
 
 <% } else { %>
 
 <% } %>
-