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>

members/migrations/0001_initial.py

@@ -0,0 +1,71 @@
+# Generated by Django 6.0.6 on 2026-07-11 22:09
+
+import django.db.models.deletion
+import phonenumber_field.modelfields
+import uuid
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Family',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('name', models.CharField(blank=True, max_length=255, verbose_name='name')),
+            ],
+            options={
+                'verbose_name': 'family',
+                'verbose_name_plural': 'families',
+                'ordering': ['name'],
+            },
+        ),
+        migrations.CreateModel(
+            name='Member',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
+                ('first_name', models.CharField(max_length=150, verbose_name='first name')),
+                ('last_name', models.CharField(max_length=150, verbose_name='last name')),
+                ('date_of_birth', models.DateField(blank=True, null=True, verbose_name='date of birth')),
+                ('email', models.EmailField(blank=True, max_length=254, verbose_name='email')),
+                ('phone', phonenumber_field.modelfields.PhoneNumberField(blank=True, max_length=128, null=True, region=None, verbose_name='phone number')),
+                ('emergency_phone', phonenumber_field.modelfields.PhoneNumberField(blank=True, max_length=128, null=True, region=None, verbose_name='emergency phone number')),
+                ('user', models.OneToOneField(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='member', to=settings.AUTH_USER_MODEL, verbose_name='user')),
+            ],
+            options={
+                'verbose_name': 'member',
+                'verbose_name_plural': 'members',
+                'ordering': ['last_name', 'first_name'],
+            },
+        ),
+        migrations.CreateModel(
+            name='FamilyMembership',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('role', models.CharField(choices=[('parent', 'parent'), ('child', 'child'), ('guardian', 'guardian'), ('other', 'other')], default='parent', max_length=255, verbose_name='role')),
+                ('family', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='memberships', to='members.family', verbose_name='family')),
+                ('member', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='family_memberships', to='members.member', verbose_name='member')),
+            ],
+            options={
+                'verbose_name': 'family membership',
+                'verbose_name_plural': 'family memberships',
+                'ordering': ['family', 'role', 'member__last_name', 'member__first_name'],
+            },
+        ),
+        migrations.AddIndex(
+            model_name='member',
+            index=models.Index(fields=['last_name', 'first_name'], name='members_mem_last_na_92a910_idx'),
+        ),
+        migrations.AlterUniqueTogether(
+            name='familymembership',
+            unique_together={('family', 'member')},
+        ),
+    ]