The metrics vhost's `/` proxied every path to VictoriaMetrics with no
auth_request, so anything that could reach metrics.<swarm> could write
(`/api/v1/import`, `/api/v1/write`, ...) and delete
(`/api/v1/admin/tsdb/delete_series`) series. Only the OTLP push route
was gated.
`/` now answers 403. The read routes Grafana's Prometheus datasource
and vmui use are forwarded by exact or `^~` prefix location, each with
the matched path as its proxy_pass URI. The bare domain, which the
swarm UI's Metrics quick link opens, redirects to vmui instead of the
store's index page. The OTLP push location is unchanged.
Closes#5186
53d0d59be0