- Add SiloEventListener class for SSE-based real-time notifications
- Add SiloPullDialog for revision selection when pulling
- Add conflict detection before pull (unsaved changes, stale revision, mtime)
- Add progress callback to _download_file() for UI feedback
- Integrate SSE listener into SiloAuthDockWidget with status indicator
- Refresh activity panel on remote change events
- Add top-level PySide.QtCore import for QThread/Signal usage