Build the club metrics

The club page now leads with its own numbers that should be zero, then the health
signals underneath.

- Teams with no coach. Not a statistic but a defect in the club's setup: with
  nobody in a management position the access service grants no authority over that
  team, so nobody can pick the squad. A physio does not count -- the query keys on
  Position.management_position, and on this season only.
- Unrostered members: active, paid, and on no team.
- Unpaid money bucketed by age. "€250 overdue past 60 days" drives a phone call;
  "€250 outstanding" does not.
- Renewal rate -- last season's actives who signed up again. Exactly computable
  because memberships are season-scoped.
- Turnout, plus the share who never responded. Silence is not an absence, so it is
  excluded from turnout and reported separately: no-response is the leading
  indicator, since it measures whether members use the app at all.

Two of these return None rather than a number, deliberately: a club in its first
season has not failed to renew anyone, and a season with no past events has no
turnout. Rendering either as 0% would libel the club, so the page says why instead.

Money is pinned to two decimals -- SQLite's Sum() drops trailing zeros, so an
aggregate rendered "€250" next to a "€0.00" constant on the same card.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

controlpanel/views.py

@@ -17,7 +17,7 @@ from .services.platform_admins import (
     revoke_platform_access,
     set_platform_access,
 )
-from .services.statistics import club_statistics, clubs_with_totals, flag_adoption, onboarding_funnel, platform_attention, platform_charts, platform_totals
+from .services.statistics import club_attention, club_charts, club_statistics, clubs_with_totals, flag_adoption, onboarding_funnel, platform_attention, platform_charts, platform_totals
 
 Flag = get_waffle_flag_model()
 Switch = get_waffle_switch_model()
@@ -95,6 +95,8 @@ class ClubDetailView(PlatformStaffRequiredMixin, DetailView):
         return super().get_context_data(
             nav="clubs",
             groups=club_statistics(self.object),
+            attention=club_attention(self.object),
+            charts=club_charts(self.object),
             admins=ClubRole.objects.filter(club=self.object, role=ClubRole.Roles.ADMIN).select_related("member", "member__user"),
             flags=flags_for_club(self.object),
             **kwargs,