Milestone: open/freeze/undergoing/completed/closed (was open/pending/deferred/progressing/closed)
Task: open/pending/undergoing/completed/closed (was open/pending/progressing/closed)
- Add MilestoneStatusEnum to schemas with typed validation
- Add started_at field to Milestone model
- Update all router/CLI references from progressing->undergoing
- Add completed status handling in task transition logic
- /notifications and /notifications/count no longer require user_id param
- return both count and unread fields for compatibility
- /notifications/read-all marks current user notifications
- /notifications/{id}/read enforces ownership (or admin)