Refactor accounts app into authentication and club apps

- Split the accounts app into new authentication and club apps for better separation of concerns.
- Migrate the custom User, Member, and Family models to the authentication app.
- Introduce Club and ClubMembership models in the club app.
- Refactor Family model to use UUID as the primary key and consolidate family-role relationships into a new FamilyMembership model.
- Update tests, managers, and migrations to align with the new structure.

club/models.py

@@ -0,0 +1,20 @@
+from django.contrib.auth.base_user import AbstractBaseUser
+from django.db import models
+from django.utils.translation import gettext_lazy as _
+
+from clubmanager.base import ClubScopedModel, UUIDModel
+
+
+class Club(UUIDModel):
+    name = models.CharField(max_length=255)
+
+    class Meta:
+        verbose_name = _("club")
+        verbose_name_plural = _("clubs")
+        ordering = ["name"]
+
+    def __str__(self):
+        return self.name
+
+
+class ClubMembership(UUIDModel): ...