chore(annotations): sync model annotations with current schema (#12245)

- Update Schema Information headers for AssignmentPolicy, Campaign,
Notification
- Reflect schema change for Campaign.template_params (not null with
default)
- Keep annotations consistent to avoid drift

app/models/notification.rb

@@ -19,6 +19,7 @@
 #
 # Indexes
 #
+#  idx_notifications_performance                   (user_id,account_id,snoozed_until,read_at)
 #  index_notifications_on_account_id               (account_id)
 #  index_notifications_on_last_activity_at         (last_activity_at)
 #  index_notifications_on_user_id                  (user_id)