Fix PyPI proxy UX and package stats calculation

- Fix artifact_count and total_size calculation to use Tags instead of
  Uploads, so PyPI cached packages show their stats correctly
- Fix PackagePage dropdown menu positioning (use fixed position with backdrop)
- Add system project detection for projects starting with "_"
- Show Version as primary column for system projects, hide Tag column
- Hide upload button for system projects (they're cache-only)
- Rename section header to "Versions" for system projects
- Fix test_projects_sort_by_name to exclude system projects from sort comparison

frontend/src/pages/PackagePage.tsx

@@ -72,6 +72,7 @@ function PackagePage() {
   const [showUploadModal, setShowUploadModal] = useState(false);
   const [showCreateTagModal, setShowCreateTagModal] = useState(false);
   const [openMenuId, setOpenMenuId] = useState<string | null>(null);
+  const [menuPosition, setMenuPosition] = useState<{ top: number; left: number } | null>(null);
 
   // Dependencies state
   const [selectedTag, setSelectedTag] = useState<TagDetail | null>(null);
@@ -100,6 +101,9 @@ function PackagePage() {
   // Derived permissions
   const canWrite = accessLevel === 'write' || accessLevel === 'admin';
 
+  // Detect system projects (convention: name starts with "_")
+  const isSystemProject = projectName?.startsWith('_') ?? false;
+
   // Get params from URL
   const page = parseInt(searchParams.get('page') || '1', 10);
   const search = searchParams.get('search') || '';
@@ -327,100 +331,209 @@ function PackagePage() {
     setSelectedTag(tag);
   };
 
-  const columns = [
-    {
-      key: 'name',
-      header: 'Tag / Version',
-      sortable: true,
-      render: (t: TagDetail) => (
-        <div className="tag-version-cell">
-          <strong
-            className={`tag-name-link ${selectedTag?.id === t.id ? 'selected' : ''}`}
-            onClick={() => handleTagSelect(t)}
-            style={{ cursor: 'pointer' }}
-          >
-            {t.name}
-          </strong>
-          {t.version && <span className="version-badge">{t.version}</span>}
-        </div>
-      ),
-    },
-    {
-      key: 'artifact_original_name',
-      header: 'Filename',
-      className: 'cell-truncate',
-      render: (t: TagDetail) => (
-        <span title={t.artifact_original_name || undefined}>{t.artifact_original_name || '-'}</span>
-      ),
-    },
-    {
-      key: 'artifact_size',
-      header: 'Size',
-      render: (t: TagDetail) => <span>{formatBytes(t.artifact_size)}</span>,
-    },
-    {
-      key: 'created_at',
-      header: 'Created',
-      sortable: true,
-      render: (t: TagDetail) => (
-        <span title={`by ${t.created_by}`}>{new Date(t.created_at).toLocaleDateString()}</span>
-      ),
-    },
-    {
-      key: 'actions',
-      header: '',
-      render: (t: TagDetail) => (
-        <div className="action-buttons">
-          <a
-            href={getDownloadUrl(projectName!, packageName!, t.name)}
-            className="btn btn-icon"
-            download
-            title="Download"
-          >
-            <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
-              <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4" />
-              <polyline points="7 10 12 15 17 10" />
-              <line x1="12" y1="15" x2="12" y2="3" />
-            </svg>
-          </a>
-          <div className="action-menu">
-            <button
-              className="btn btn-icon"
-              onClick={(e) => {
-                e.stopPropagation();
-                setOpenMenuId(openMenuId === t.id ? null : t.id);
-              }}
-              title="More actions"
+  const handleMenuOpen = (e: React.MouseEvent, tagId: string) => {
+    e.stopPropagation();
+    if (openMenuId === tagId) {
+      setOpenMenuId(null);
+      setMenuPosition(null);
+    } else {
+      const rect = e.currentTarget.getBoundingClientRect();
+      setMenuPosition({ top: rect.bottom + 4, left: rect.right - 180 });
+      setOpenMenuId(tagId);
+    }
+  };
+
+  // System projects show Version first, regular projects show Tag first
+  const columns = isSystemProject
+    ? [
+        // System project columns: Version first, then Filename
+        {
+          key: 'version',
+          header: 'Version',
+          sortable: true,
+          render: (t: TagDetail) => (
+            <strong
+              className={`tag-name-link ${selectedTag?.id === t.id ? 'selected' : ''}`}
+              onClick={() => handleTagSelect(t)}
+              style={{ cursor: 'pointer' }}
             >
-              <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
-                <circle cx="12" cy="12" r="1" />
-                <circle cx="12" cy="5" r="1" />
-                <circle cx="12" cy="19" r="1" />
-              </svg>
+              <span className="version-badge">{t.version || t.name}</span>
+            </strong>
+          ),
+        },
+        {
+          key: 'artifact_original_name',
+          header: 'Filename',
+          className: 'cell-truncate',
+          render: (t: TagDetail) => (
+            <span title={t.artifact_original_name || t.name}>{t.artifact_original_name || t.name}</span>
+          ),
+        },
+        {
+          key: 'artifact_size',
+          header: 'Size',
+          render: (t: TagDetail) => <span>{formatBytes(t.artifact_size)}</span>,
+        },
+        {
+          key: 'created_at',
+          header: 'Cached',
+          sortable: true,
+          render: (t: TagDetail) => (
+            <span>{new Date(t.created_at).toLocaleDateString()}</span>
+          ),
+        },
+        {
+          key: 'actions',
+          header: '',
+          render: (t: TagDetail) => (
+            <div className="action-buttons">
+              <a
+                href={getDownloadUrl(projectName!, packageName!, t.name)}
+                className="btn btn-icon"
+                download
+                title="Download"
+              >
+                <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                  <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4" />
+                  <polyline points="7 10 12 15 17 10" />
+                  <line x1="12" y1="15" x2="12" y2="3" />
+                </svg>
+              </a>
+              <button
+                className="btn btn-icon"
+                onClick={(e) => handleMenuOpen(e, t.id)}
+                title="More actions"
+              >
+                <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                  <circle cx="12" cy="12" r="1" />
+                  <circle cx="12" cy="5" r="1" />
+                  <circle cx="12" cy="19" r="1" />
+                </svg>
+              </button>
+            </div>
+          ),
+        },
+      ]
+    : [
+        // Regular project columns: Tag, Version, Filename
+        {
+          key: 'name',
+          header: 'Tag',
+          sortable: true,
+          render: (t: TagDetail) => (
+            <strong
+              className={`tag-name-link ${selectedTag?.id === t.id ? 'selected' : ''}`}
+              onClick={() => handleTagSelect(t)}
+              style={{ cursor: 'pointer' }}
+            >
+              {t.name}
+            </strong>
+          ),
+        },
+        {
+          key: 'version',
+          header: 'Version',
+          render: (t: TagDetail) => (
+            <span className="version-badge">{t.version || '—'}</span>
+          ),
+        },
+        {
+          key: 'artifact_original_name',
+          header: 'Filename',
+          className: 'cell-truncate',
+          render: (t: TagDetail) => (
+            <span title={t.artifact_original_name || undefined}>{t.artifact_original_name || '—'}</span>
+          ),
+        },
+        {
+          key: 'artifact_size',
+          header: 'Size',
+          render: (t: TagDetail) => <span>{formatBytes(t.artifact_size)}</span>,
+        },
+        {
+          key: 'created_at',
+          header: 'Created',
+          sortable: true,
+          render: (t: TagDetail) => (
+            <span title={`by ${t.created_by}`}>{new Date(t.created_at).toLocaleDateString()}</span>
+          ),
+        },
+        {
+          key: 'actions',
+          header: '',
+          render: (t: TagDetail) => (
+            <div className="action-buttons">
+              <a
+                href={getDownloadUrl(projectName!, packageName!, t.name)}
+                className="btn btn-icon"
+                download
+                title="Download"
+              >
+                <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                  <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4" />
+                  <polyline points="7 10 12 15 17 10" />
+                  <line x1="12" y1="15" x2="12" y2="3" />
+                </svg>
+              </a>
+              <button
+                className="btn btn-icon"
+                onClick={(e) => handleMenuOpen(e, t.id)}
+                title="More actions"
+              >
+                <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                  <circle cx="12" cy="12" r="1" />
+                  <circle cx="12" cy="5" r="1" />
+                  <circle cx="12" cy="19" r="1" />
+                </svg>
+              </button>
+            </div>
+          ),
+        },
+      ];
+
+  // Find the tag for the open menu
+  const openMenuTag = tags.find(t => t.id === openMenuId);
+
+  // Close menu when clicking outside
+  const handleClickOutside = () => {
+    if (openMenuId) {
+      setOpenMenuId(null);
+      setMenuPosition(null);
+    }
+  };
+
+  // Render dropdown menu as a portal-like element
+  const renderActionMenu = () => {
+    if (!openMenuId || !menuPosition || !openMenuTag) return null;
+    const t = openMenuTag;
+    return (
+      <div
+        className="action-menu-backdrop"
+        onClick={handleClickOutside}
+      >
+        <div
+          className="action-menu-dropdown"
+          style={{ top: menuPosition.top, left: menuPosition.left }}
+          onClick={(e) => e.stopPropagation()}
+        >
+          <button onClick={() => { navigator.clipboard.writeText(t.artifact_id); setOpenMenuId(null); setMenuPosition(null); }}>
+            Copy Artifact ID
+          </button>
+          <button onClick={() => { fetchEnsureFileForTag(t.name); setOpenMenuId(null); setMenuPosition(null); }}>
+            View Ensure File
+          </button>
+          {canWrite && (
+            <button onClick={() => { setCreateTagArtifactId(t.artifact_id); setShowCreateTagModal(true); setOpenMenuId(null); setMenuPosition(null); }}>
+              Create/Update Tag
             </button>
-            {openMenuId === t.id && (
-              <div className="action-menu-dropdown">
-                <button onClick={() => { navigator.clipboard.writeText(t.artifact_id); setOpenMenuId(null); }}>
-                  Copy Artifact ID
-                </button>
-                <button onClick={() => { fetchEnsureFileForTag(t.name); setOpenMenuId(null); }}>
-                  View Ensure File
-                </button>
-                {canWrite && (
-                  <button onClick={() => { setCreateTagArtifactId(t.artifact_id); setShowCreateTagModal(true); setOpenMenuId(null); }}>
-                    Create/Update Tag
-                  </button>
-                )}
-                <button onClick={() => { handleTagSelect(t); setOpenMenuId(null); }}>
-                  View Dependencies
-                </button>
-              </div>
-            )}
-          </div>
+          )}
+          <button onClick={() => { handleTagSelect(t); setOpenMenuId(null); setMenuPosition(null); }}>
+            View Dependencies
+          </button>
         </div>
-      ),
-    },
-  ];
+      </div>
+    );
+  };
 
   if (loading && !tagsData) {
     return <div className="loading">Loading...</div>;
@@ -463,7 +576,7 @@ function PackagePage() {
           <div className="page-header__title-row">
             <h1>{packageName}</h1>
             {pkg && <Badge variant="default">{pkg.format}</Badge>}
-            {user && canWrite && (
+            {user && canWrite && !isSystemProject && (
               <button
                 className="btn btn-primary btn-small header-upload-btn"
                 onClick={() => setShowUploadModal(true)}
@@ -523,7 +636,7 @@ function PackagePage() {
 
 
       <div className="section-header">
-        <h2>Tags / Versions</h2>
+        <h2>{isSystemProject ? 'Versions' : 'Tags / Versions'}</h2>
       </div>
 
       <div className="list-controls">
@@ -902,6 +1015,9 @@ function PackagePage() {
           </div>
         </div>
       )}
+
+      {/* Action Menu Dropdown */}
+      {renderActionMenu()}
     </div>
   );
 }