When a helm chart index has download URLs on a different host than the
remote's base URL (e.g. charts hosted on intel.github.io but downloads
on github.com), the URL rewriting would produce broken proxy URLs.
Now URLs with a different host are left as-is so helm downloads
directly from the source. Same-host URLs are still rewritten through
the proxy as before.
Also fixes the route prefix to use /local/ for local members.
## Summary
- Virtual engine detects local members and generates indexes in-memory
- MemberIndex.RepoType drives correct URL prefix in merged output
- PyPI merger rewrites links to /api/v1/local/ or /api/v1/remote/ appropriately
- Includes local PyPI support (cherry-picked from #50)
## Test plan
- [x] Upload wheel to local PyPI → install from direct local URL
- [x] Create virtual with local + remote → install from virtual URL
- [x] Both paths produce correct absolute download URLs
Reviewed-on: #51
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>