* Mount web UI under /ui (closes#123)
The UI now lives under /ui so reverse proxies can apply different
access rules to it (e.g. require auth) while leaving the package
endpoints (/npm, /pypi, /v2, ...) open to build machines.
- GET / redirects to /ui/
- /api/browse and /api/compare move to /ui/api/browse and
/ui/api/compare since only the browser JS calls them
- /health, /stats, /metrics, /openapi.json and /api/* stay at root
* README: nginx example for splitting UI auth from package endpoints
The /ui prefix lets a reverse proxy apply different access rules to the
web UI than to the package endpoints. Adds the snippet that motivated
the prefix change so deployers don't have to derive it.
