- Add tests for cascade deletion ref_count (package/project delete)
- Add tests for tag update ref_count adjustments
- Fix resumable upload bug where ref_count was incremented manually AND by SQL trigger
- ref_count is now exclusively managed by SQL triggers on tag INSERT/DELETE/UPDATE
- Add test_integration_uploads.py with 12 tests for duplicate upload scenarios
- Add test_ref_count.py with 7 tests for ref_count management
- Fix ArtifactDetailResponse to include sha256 and checksum fields
- Fix health check SQL warning by wrapping in text()
- Update tests to use unique content per test run for idempotency