feat(multi-tenancy): implement critical fixes for orphaned users and permissions

- Simplified HasTenantAccess permission logic to ensure every authenticated user has an account.
- Added fallback to system account for OpenAI settings in AI configuration.
- Allowed any authenticated user to check task progress in IntegrationSettingsViewSet.
- Created a script to identify and fix orphaned users without accounts.
- Updated error response handling in business endpoints for clarity.

backend/igny8_core/auth/serializers.py

@@ -80,6 +80,10 @@ class SiteSerializer(serializers.ModelSerializer):
             'created_at', 'updated_at'
         ]
         read_only_fields = ['created_at', 'updated_at', 'account']
+        # Explicitly specify required fields for clarity
+        extra_kwargs = {
+            'industry': {'required': True, 'error_messages': {'required': 'Industry is required when creating a site.'}},
+        }
     
     def __init__(self, *args, **kwargs):
         """Allow partial updates for PATCH requests."""
@@ -87,10 +91,12 @@ class SiteSerializer(serializers.ModelSerializer):
         # Make slug optional - it will be auto-generated from name if not provided
         if 'slug' in self.fields:
             self.fields['slug'].required = False
-        # For partial updates (PATCH), make name optional
+        # For partial updates (PATCH), make name and industry optional
         if self.partial:
             if 'name' in self.fields:
                 self.fields['name'].required = False
+            if 'industry' in self.fields:
+                self.fields['industry'].required = False
     
     def validate_domain(self, value):
         """Ensure domain has https:// protocol.