Add Spinner, a Minecraft hostname-routing reverse proxy

Routes Java Edition connections by the hostname in the handshake, with
wildcard domains, backend failover, PROXY protocol v2, cached server-list
status from health probes, hot-reloaded config, and an admin page and
metrics endpoint. Includes CI, tagged releases and a container image.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

go.sum

@@ -0,0 +1,2 @@
+git.veillax.com/Veillax/reef v0.1.7 h1:5C2udonlJac2xvDOE5e+zDxej+AbZ9ttrNSE4owmwuU=
+git.veillax.com/Veillax/reef v0.1.7/go.mod h1:ZBUd/BARO5kkpUNTP81TTY1aQXLHFR6bKDhCxckjHso=