Improve dependency UI: rename to DependGraph, hide empty Used By

- Rename "Dependency Graph" modal title to "DependGraph"
- Hide "Used By" section when no packages depend on this package

frontend/src/components/DependencyGraph.tsx

@@ -247,7 +247,7 @@ function DependencyGraph({ projectName, packageName, tagName, onClose }: Depende
     <div className="dependency-graph-modal" onClick={onClose}>
       <div className="dependency-graph-content" onClick={e => e.stopPropagation()}>
         <div className="dependency-graph-header">
-          <h2>Dependency Graph</h2>
+          <h2>DependGraph</h2>
           <div className="dependency-graph-info">
             <span>{projectName}/{packageName} @ {tagName}</span>
             {resolution && (