As a user, I want to track changes and access previous versions of the proposal so that I can review the history and revert to earlier versions if needed.
Acceptance Criteria:
* The system tracks all changes made to the proposal.
* Users can access a history of changes with timestamps and user information.
* Previous versions of the proposal are saved and can be restored.
* Users can compare different versions to see what has changed.
* The system highlights changes between versions.
* Notifications are sent when a new version is saved.
* Users can add comments or notes to specific versions.