- 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
