feat: replace email flows with in-app notifications

Add recipient notification detail and filtering, a queued admin composer, and contextual automatic titles. Retire email delivery, obsolete auth routes, newsletter data, and related templates and settings.

config/settings/development.py

@@ -29,9 +29,6 @@ SECURE_CONTENT_TYPE_NOSNIFF = False
 SECURE_BROWSER_XSS_FILTER = False
 X_FRAME_OPTIONS = "SAMEORIGIN"
 
-# Email backend for development
-EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
-
 # Disable caching in development
 CACHES = {
     'default': {