Add parent claims: onboarding a roster of children with no parents on file

The migration path for a club arriving with a list of children from a
federation export and no parent records. Children import without logins, each
into a family of their own -- that shape *is* the "nobody is responsible for
this child" state, so there's no unclaimed flag to drift out of step with
reality, and a family drops off the worklist by itself the moment a parent
joins it. `family_role=child` with a blank `family_group` asks for that; any
other lone role is still a mistake in the file.

Verification is a human decision, deliberately. A parent submits a public form
with the child's name and date of birth as free text -- no search, no
autocomplete, and the same response whether or not the child was found, because
the page needs no login and anything that resolved the child would turn it into
a way to enumerate the club's children. An admin matches it from a queue
against a shortlist that only ever contains children with nobody on file, so
approving can never quietly re-parent a child who already has one.

The alternatives were worse. A claim code needs a delivery channel the club may
not have and is a bearer token besides. Matching on name plus birthday hands out
someone else's child to whoever guesses a birthday. The club is the only party
that actually knows its own families.

That form is also the registration: open self-registration is now closed
(shadowing account_signup rather than removing the route, so the URL name
allauth's templates reverse still resolves). The account is created on
approval, not on submission, so a public form can't fill the user table. An
approved parent lands as a guardian -- login and family link, no membership, no
fee -- gets a password-reset link, and a minimal "my family" page.

One bug worth recording: families_awaiting_a_parent first used
annotate(Count(..., filter=...)) over a queryset already filtered on the same
join, so Django reused that join for the counts and a parent with no
ClubMembership of their own -- exactly what a newly linked guardian is -- went
uncounted, leaving the family unclaimed forever. Exists subqueries avoid it. A
test pins both directions.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

rosterchief/urls.py

@@ -16,7 +16,7 @@ from django.views.generic import RedirectView
 from django.views.static import serve
 
 from api.urls import api
-from club.views import root
+from club.views import root, signup_closed
 
 from .health import healthz
 
@@ -25,7 +25,13 @@ urlpatterns = [
     path("healthz", healthz, name="healthz"),
     path("admin/login/", RedirectView.as_view(pattern_name="account_login", query_string=True), name="admin_login_redirect"),
     path("admin/", admin.site.urls),
+    # Before allauth's own urls so it wins the match: self-registration is closed.
+    # Accounts are created by an admin, by the family-registration form, or by an
+    # approved parent claim (members/views.py) -- a club has no reason to let a
+    # stranger create one, and the claim queue would be the first thing to suffer.
+    path("accounts/signup/", signup_closed, name="account_signup"),
     path("accounts/", include("allauth.urls")),
+    path("", include("members.urls")),
     path("controlpanel/", include("controlpanel.urls")),
     path("manage/", include("management.urls")),
     path("api/v1/", api.urls),