- Extend sseClient with userID, workstationID, and item filter set
- Update Subscribe() to accept userID and workstationID params
- Add WatchItem/UnwatchItem/IsWatchingItem methods on sseClient
- Add PublishToItem, PublishToWorkstation, PublishToUser targeted delivery
- Targeted events get IDs but skip history ring buffer (real-time only)
- Update HandleEvents to pass auth user ID and workstation_id query param
- Touch workstation last_seen on SSE connect
- Existing Publish() broadcast unchanged; all current callers unaffected
- Add 5 new tests for targeted delivery and item watch lifecycle
Closes#162