feat: wire TUI settings to backend + pgzip consistency

- Add native engine support for restore (cmd/native_restore.go)
- Integrate native engine restore into cmd/restore.go with fallback
- Fix CPUWorkloadType to auto-detect CPU if CPUInfo is nil
- Replace standard gzip with pgzip in native_backup.go
- All compression now uses parallel pgzip consistently

Bump version to 5.4.2

main.go

@@ -16,7 +16,7 @@ import (
 
 // Build information (set by ldflags)
 var (
-	version   = "5.4.1"
+	version   = "5.4.2"
 	buildTime = "unknown"
 	gitCommit = "unknown"
 )