Refactor user account system and remove moderation integration

- Remove first_name and last_name fields from User model
- Add user deletion and social provider services
- Restructure auth serializers into separate directory
- Update avatar upload functionality and API endpoints
- Remove django-moderation integration documentation
- Add mandatory compliance enforcement rules
- Update frontend documentation with API usage examples

backend/apps/parks/management/commands/seed_sample_data.py

@@ -1030,8 +1030,7 @@ class Command(BaseCommand):
                 username="testuser",
                 defaults={
                     "email": "test@example.com",
-                    "first_name": "Test",
-                    "last_name": "User",
+                    "display_name": "Test User",
                 },
             )
             if created: