Unit Tests / test (push) Successful in 10s
## Summary - Closes #16 - Confirms `/preview_email/<pk>/` requires an authenticated user (`@login_required` already on the view) - Adds unit tests for unauthenticated redirect and authenticated preview access ## Test plan - [x] `python manage.py test public.tests.PreviewEmailAuthTests` - [ ] Manually hit `/preview_email/1/` logged out → redirect to `/accounts/login/` - [ ] Log in and hit same URL → email preview renders Reviewed-on: #17