feat: agrega rol 'publico' con UserProfile y permisos diferenciados

- Crea modelo UserProfile (OneToOne con User) con user_type: publico/user/administrator
- Señal post_save que crea UserProfile automáticamente al crear User
- UserSerializer.get_role() lee desde profile.user_type
- Nuevos permisos: IsNotPublico, IsPublico y actualiza IsAdministrator
- IsNotPublico restringe acceso a vistas de gestión (productos, clientes, ventas)
- CatalogSaleView.create permite publico; otras acciones requieren IsNotPublico
- UserProfile inline en admin de Usuarios
- Data migration para backfill de usuarios existentes

tienda_ilusion/users/migrations/0001_initial.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.0.6 on 2026-06-22 17:26
+
+import django.db.models.deletion
+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='UserProfile',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('user_type', models.CharField(choices=[('publico', 'Público'), ('user', 'Usuario'), ('administrator', 'Administrador')], default='user', max_length=20)),
+                ('user', models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, related_name='profile', to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

tienda_ilusion/users/migrations/0002_backfill_user_profiles.py

@@ -0,0 +1,24 @@
+from django.db import migrations
+
+
+def backfill_user_profiles(apps, schema_editor):
+    User = apps.get_model("auth", "User")
+    UserProfile = apps.get_model("users", "UserProfile")
+    for user in User.objects.all():
+        UserProfile.objects.get_or_create(
+            user=user,
+            defaults={
+                "user_type": "administrator" if user.is_staff else "user",
+            },
+        )
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.RunPython(backfill_user_profiles, migrations.RunPython.noop),
+    ]