Notify User When Feedback Receives Comments or Upvotes

As a feedback author I want to be notified when someone comments on my feedback or upvotes it So that I can engage with the community discussion and see if my idea is getting traction Acceptance Criteria: New comment notification includes commenter name and preview of comment text Upvote notifications are batched (e.g., "3 people upvoted your feedback") rather than 1:1 Notifications appear in-app and optionally via email Comment notifications are sent to all involved commenters (thread participants), not just the OP User can disable comment/upvote notifications in settings