feat: add automation condition to filter private notes (#12102)

## Summary

Adds a new automation condition to filter private notes.

This allows automation rules to explicitly include or exclude private
notes instead of relying on implicit behavior.

Fixes: #11208 

## Preview



https://github.com/user-attachments/assets/c40f6910-7bbf-4e59-aae5-ad408602927a

app/javascript/dashboard/helper/automationHelper.js

@@ -150,6 +150,7 @@ export const getConditionOptions = ({
     conversation_language: languages,
     country_code: countries,
     message_type: messageTypeOptions,
+    private_note: booleanFilterOptions,
     priority: priorityOptions,
     labels: generateConditionOptions(labels, 'title'),
   };