Fix circular dependency detection and hide empty graph modal

- Add artifact-level self-dependency check (skip if dep resolves to same artifact)
- Close dependency graph modal if package has no dependencies to show
  (only root package with no children and no missing deps)

backend/app/dependencies.py

@@ -791,6 +791,11 @@ def resolve_dependencies(
                 continue
 
             dep_artifact_id, dep_version, dep_size = resolved_dep
+
+            # Skip if resolved to same artifact (self-dependency at artifact level)
+            if dep_artifact_id == artifact_id:
+                continue
+
             _resolve_recursive(
                 dep_artifact_id,
                 dep.dependency_project,