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/admin.py

@@ -0,0 +1,61 @@
+from django.contrib import admin
+from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
+
+from .forms import UserChangeForm, UserCreationForm
+from .models import Family, Guardianship, Member, User
+
+
+@admin.register(User)
+class UserAdmin(BaseUserAdmin):
+    add_form = UserCreationForm
+    form = UserChangeForm
+    model = User
+
+    list_display = ("email", "is_staff", "is_superuser", "is_active")
+    list_filter = ("is_staff", "is_superuser", "is_active", "groups")
+    search_fields = ("email",)
+    ordering = ("email",)
+
+    fieldsets = (
+        (None, {"fields": ("email", "password")}),
+        ("Permissions", {"fields": ("is_active", "is_staff", "is_superuser", "groups", "user_permissions")}),
+        ("Important dates", {"fields": ("last_login", "date_joined")}),
+    )
+    add_fieldsets = (
+        (None, {
+            "classes": ("wide",),
+            "fields": ("email", "usable_password", "password1", "password2"),
+        }),
+    )
+
+
+class GuardianshipInline(admin.TabularInline):
+    """Guardians of a member (edit from the child's page)."""
+
+    model = Guardianship
+    fk_name = "child"
+    extra = 0
+    autocomplete_fields = ("guardian",)
+
+
+class MemberInline(admin.TabularInline):
+    model = Member
+    extra = 0
+    fields = ("first_name", "last_name", "date_of_birth", "license_number")
+    show_change_link = True
+
+
+@admin.register(Member)
+class MemberAdmin(admin.ModelAdmin):
+    list_display = ("last_name", "first_name", "date_of_birth", "license_number", "family", "user")
+    list_filter = ("family",)
+    search_fields = ("first_name", "last_name", "email", "license_number")
+    autocomplete_fields = ("user", "family")
+    inlines = (GuardianshipInline,)
+
+
+@admin.register(Family)
+class FamilyAdmin(admin.ModelAdmin):
+    list_display = ("name", "address")
+    search_fields = ("name",)
+    inlines = (MemberInline,)