Migrate service control from ZMQ to SSH with real-time progress

Replace ZMQ-based service start/stop commands with SSH execution in tmux
popups. This provides better user feedback with real-time systemctl output
while eliminating blocking operations from the main message processing loop.

Changes:
- Service start/stop now use SSH with progress display
- Added backup functionality with 'B' key
- Preserved transitional icons (↑/↓) for immediate visual feedback
- Removed all ZMQ service control commands and handlers
- Updated configuration to include backup_alias setting
- All operations (rebuild, backup, services) now use consistent SSH interface

This ensures stable heartbeat processing while providing superior user
experience with live command output and service status feedback.

CLAUDE.md

@@ -49,8 +49,12 @@ hostname2 = [
 ### Navigation
 - **Tab**: Switch between hosts
 - **↑↓ or j/k**: Select services
+- **s**: Start selected service (UserStart)
+- **S**: Stop selected service (UserStop)
 - **J**: Show service logs (journalctl)
 - **L**: Show custom log files
+- **R**: Rebuild current host
+- **B**: Run backup on current host
 - **q**: Quit dashboard
 
 ## Core Architecture Principles