🥅(backend) catch request timeout and Brevo contact addition errors

Handle unhandled exceptions to prevent UX impact. Marketing email operations
are optional and should not disrupt core functionality.

My first implementation was imperfect, raising error in sentry.

src/backend/core/services/marketing.py

@@ -10,6 +10,7 @@ from django.core.exceptions import ImproperlyConfigured
 from django.utils.module_loading import import_string
 
 import brevo_python
+import requests
 
 logger = logging.getLogger(__name__)
 
@@ -120,7 +121,7 @@ class BrevoMarketingService:
 
         try:
             response = contact_api.create_contact(contact, **api_configurations)
-        except brevo_python.rest.ApiException as err:
+        except (brevo_python.rest.ApiException, requests.exceptions.ReadTimeout) as err:
             logger.exception("Failed to create contact in Brevo")
             raise ContactCreationError("Failed to create contact in Brevo") from err