Remove service restart functionality and make R always rebuild host

Simplified keyboard controls by removing service restart functionality:

- Removed 'r' key restart functionality from Services panel
- Made 'R' key always trigger system rebuild regardless of focused panel
- Updated context shortcuts to show 'R: Rebuild Host' globally
- Removed all ServiceRestart enum variants and associated code:
  - UiCommand::ServiceRestart
  - CommandType::ServiceRestart
  - ServiceAction::Restart
- Cleaned up pending transition logic to only handle Start/Stop commands

The 'R' key now consistently rebuilds the current host from any panel,
while 's' and 'S' continue to handle service start/stop in Services panel.

dashboard/src/ui/widgets/services.rs

@@ -134,7 +134,6 @@ impl ServicesWidget {
         if let Some((command_type, _original_status, _start_time)) = pending_transitions.get(service_name) {
             // Show transitional icons for pending commands
             let (icon, status_text) = match command_type {
-                CommandType::ServiceRestart => ("↻", "restarting"),
                 CommandType::ServiceStart => ("↑", "starting"), 
                 CommandType::ServiceStop => ("↓", "stopping"),
                 _ => return (StatusIcons::get_icon(info.widget_status).to_string(), info.status.clone(), Theme::status_color(info.widget_status)), // Not a service command