fix: update ua in invoke, not constructor

[Crypta-Eve]

With the UA check in the constructor, new installs would fail with the following error as migrations were unable to run.

front-2-1      | 
front-2-1      | In Connection.php line 829:
front-2-1      |
front-2-1      |   SQLSTATE[42S02]: Base table or view not found: 1146 Table 'seat2.global_set
front-2-1      |   tings' doesn't exist (Connection: mysql, SQL: select value from global_s  
front-2-1      |   ettings where name = admin_contact limit 1)
front-2-1      |
front-2-1      | 

This also means the admin contact email change will apply immediately, so can revert eveseat/web#696 and eveseat/docs#183.