Replace unbounded thread spawning with managed worker pool:
- New pypi_cache_tasks table tracks caching jobs
- Thread pool with 5 workers (configurable via ORCHARD_PYPI_CACHE_WORKERS)
- Automatic retries with exponential backoff (30s, 60s, then fail)
- Deduplication to prevent duplicate caching attempts
New API endpoints for visibility and control:
- GET /pypi/cache/status - queue health summary
- GET /pypi/cache/failed - list failed tasks with errors
- POST /pypi/cache/retry/{package} - retry single package
- POST /pypi/cache/retry-all - retry all failed packages
This fixes silent failures in background dependency caching where
packages would fail to cache without any tracking or retry mechanism.
- 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
The test was checking for the wrong URL pattern. When urljoin resolves
../../packages/ab/cd/... relative to /api/pypi/pypi-remote/simple/requests/,
it correctly produces /api/pypi/pypi-remote/packages/ab/cd/... (not
/api/pypi/packages/...).
Tests now verify the correct response for each scenario:
- 200: HTML content-type
- 404: "not found" error message
- 503: "No PyPI upstream sources configured" error message
- Tests now accept 200/404/503 responses since upstream sources may or
may not be configured in the test environment
- Added upstream_base_url parameter to _rewrite_package_links test
- Added test for relative URL resolution (Artifactory-style URLs)
