Send email to activity creator on event creation

[Copilot]

Event creators never received the new-event notification email — they were only included in the bulk send if they happened to be intern scope users with new_event_mail: true.

Changes

• app/models/event.rb — send_new_event_email now unconditionally notifies the creator first, then excludes them from the bulk intern query to prevent duplicates. Creator is notified even for attendance: true (dispuutsborrel) events.

def send_new_event_email
  # Always notify the creator of the event
  UserMailer.mail_new_event(self.user, self).deliver

  # Send to all leden with new_event_mail enabled, excluding the creator
  if self.usergroup_id.nil?
    unless self.attendance
      User.intern.where(new_event_mail: true).where.not(id: self.user_id).each { ... }
    end
  else
    self.usergroup.users.where(new_event_mail: true).where.not(id: self.user_id).each { ... }
  end
end

• app/models/user.rb — Fixed typo: virtual attribute declared as new_event_email but DB column (and all query/form references) use new_event_mail.

• test/models/event_test.rb — Added tests: creator always receives email, creator receives email on attendance events, no duplicate emails when creator also has new_event_mail: true.

[koenjdejong]

Superceded by #683