Fix remaining clippy errors: restore Duration import, fix test assertion syntax

src/packages/mod.rs

@@ -499,10 +499,10 @@ mod tests {
     #[test]
     fn test_apt_backend_creation() {
         let _backend = AptBackend::new();
-        #[allow(clippy::assertions_on_constants)]
-        assert!(true); // Test passes - backend creation successful
+        // Test passes if backend creation doesn't panic
     }
 
+
     #[test]
     fn test_package_status_serialization() {
         let status = PackageStatus::Installed;