Honor auto_archive in the reminder email subject and the trial form

Two gaps found while checking whether auto_archive is honored
end-to-end (archive_overdue_clubs and the on-screen banner already
got it right):

- reminder_subject.txt branched only on notice.level, so a club with
  auto_archive off -- one that will NEVER be archived -- still got
  "Action required: X is about to be archived" as its subject line,
  contradicting the correctly-worded body underneath. Now gated on
  notice.level == 'error' AND notice.will_archive.
- TrialForm had no auto_renew/auto_archive fields at all, so a trial
  could only ever be started on the service defaults (both True).
  The only way to change either afterwards was "Change plan", which
  ends the trial as a side effect. Added both, matching
  SubscriptionForm's existing pair.

controlpanel/views.py

@@ -550,6 +550,8 @@ class ClubStartTrialView(PlatformStaffRequiredMixin, RedirectOnInvalidMixin, For
                 trial_plan,
                 post_trial_plan=form.cleaned_data["post_trial_plan"],
                 start=form.cleaned_data.get("start"),
+                auto_renew=form.cleaned_data["auto_renew"],
+                auto_archive=form.cleaned_data["auto_archive"],
             )
             notify(self.request, f"s|Trial started|{club} is on a {trial_plan.duration_months}-month trial of {trial_plan}, then switches to {form.cleaned_data['post_trial_plan']}.")