Add http_client field to AppState, initialized once at startup.
Replace per-request Client::builder() calls in npm, maven, pypi,
and docker registry handlers with the shared instance.
This reuses the connection pool across requests instead of
creating a new client on every proxy fetch.
Bump version to 0.2.20.
- Add repo_index.rs with lazy rebuild on write operations
- Double-checked locking to prevent race conditions
- npm optimization: count tarballs instead of parsing metadata.json
- Add pagination to all registry list pages (?page=1&limit=50)
- Invalidate index on PUT/proxy cache in docker/maven/npm/pypi
Performance: 500-800x faster list page loads after first rebuild
- Add DashboardMetrics for tracking downloads/uploads/cache hits per registry
- Add ActivityLog for recent activity with bounded size (50 entries)
- Instrument Docker, npm, Maven, and Cargo handlers with metrics
- Add /api/ui/dashboard endpoint with global stats and activity
- Implement dark theme dashboard with real-time polling (5s interval)
- Add mount points table showing registry paths and proxy upstreams
