Add accounts app: custom User, Member, families & guardianship

Introduce the foundational accounts app:
- Custom email-as-username User (AbstractBaseUser + PermissionsMixin) set
  as AUTH_USER_MODEL, decoupled from membership so children can be members
  without a login.
- Member model holding personal/roster data (names, contact email, phone +
  emergency phone via django-phonenumber-field, license number, DOB) with an
  optional link to a User.
- Family household grouping and directional Guardianship (guardian -> child)
  with uniqueness and no-self-guardian constraints.
- Custom UserAdmin plus Member/Family admin with inlines and autocomplete.
- Settings: register apps, AUTH_USER_MODEL, phonenumber defaults (BE/E164).
- Add CLAUDE.md and a tracked static/ directory.

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

accounts/managers.py

@@ -0,0 +1,32 @@
+from django.contrib.auth.base_user import BaseUserManager
+
+
+class UserManager(BaseUserManager):
+    """Manager for the email-based custom User model."""
+
+    use_in_migrations = True
+
+    def _create_user(self, email, password, **extra_fields):
+        if not email:
+            raise ValueError("Users must have an email address.")
+        email = self.normalize_email(email)
+        user = self.model(email=email, **extra_fields)
+        user.set_password(password)
+        user.save(using=self._db)
+        return user
+
+    def create_user(self, email, password=None, **extra_fields):
+        extra_fields.setdefault("is_staff", False)
+        extra_fields.setdefault("is_superuser", False)
+        return self._create_user(email, password, **extra_fields)
+
+    def create_superuser(self, email, password=None, **extra_fields):
+        extra_fields.setdefault("is_staff", True)
+        extra_fields.setdefault("is_superuser", True)
+
+        if extra_fields.get("is_staff") is not True:
+            raise ValueError("Superuser must have is_staff=True.")
+        if extra_fields.get("is_superuser") is not True:
+            raise ValueError("Superuser must have is_superuser=True.")
+
+        return self._create_user(email, password, **extra_fields)