Complete people-domain move into members app; keep names on Member

Finish relocating Member/Family/FamilyMembership from authentication into
a dedicated members app, and revert the half-applied move of member names
onto the global User.

- members: add first_name/last_name back to Member (the whole codebase —
  tests, CSV importer, club app, admin — assumes them, and login-less
  children in families need a name); restore local ordering/index and the
  member__last_name lookups in Family.__str__ and FamilyMembership.
- authentication: drop first_name/last_name from User; get_full_name/
  get_short_name delegate to the linked member, else fall back to email.
- migrations: create members.0001_initial, repoint club.ClubMembership FK
  (club.0005), delete the models from authentication (0004, rewritten to
  plain DeleteModel ops in child-first order to avoid a SQLite table-remake
  crash).
- fix stale imports across apps (authentication/club tests, CSV importer)
  and missing imports/URLs in members tests; add missing _ import in
  members/admin.py; export MemberCsvImporter from members.services.

Full suite green (64 tests), ruff clean.

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

club/apps.py

@@ -2,4 +2,4 @@ from django.apps import AppConfig
 
 
 class ClubConfig(AppConfig):
-    name = 'club'
+    name = "club"

club/migrations/0005_alter_clubmembership_member.py

@@ -0,0 +1,20 @@
+# Generated by Django 6.0.6 on 2026-07-11 22:09
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('club', '0004_alter_clubmembership_license'),
+        ('members', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='clubmembership',
+            name='member',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='member_of', to='members.member', verbose_name='member'),
+        ),
+    ]

club/models.py

@@ -1,9 +1,8 @@
-from django.contrib.auth.base_user import AbstractBaseUser
 from django.db import models
 from django.utils.translation import gettext_lazy as _
 
-from authentication.models import Member
-from clubmanager.base import ClubScopedModel, UUIDModel
+from clubmanager.base import UUIDModel
+from members.models import Member
 
 
 class Club(UUIDModel):

club/tests.py

@@ -3,7 +3,7 @@ import uuid
 from django.db import IntegrityError
 from django.test import TestCase
 
-from authentication.models import Member
+from members.models import Member
 
 from .models import Club, ClubMembership