fix(email): stay silent when SMTP notifications are disabled

The event subscriber is registered unconditionally and only checked the per-event list (smtpEnabledEvents, default login.attempt,cpu.high) — not the smtpEnable master toggle. Login events are always published, so a panel with smtpEnable=false still attempted a send on every login and logged 'email subscriber: send failed: smtp host not configured'. Gate HandleEvent on GetSmtpEnable() so a disabled-SMTP panel does nothing, matching the comment where the subscriber is registered.

internal/web/service/email/subscriber.go

@@ -31,6 +31,9 @@ func NewSubscriber(settingService service.SettingService, emailService *EmailSer
 
 // HandleEvent is the eventbus subscriber callback.
 func (s *Subscriber) HandleEvent(e eventbus.Event) {
+	if on, err := s.settingService.GetSmtpEnable(); err != nil || !on {
+		return
+	}
 	if !s.isEventEnabled(e.Type) {
 		return
 	}