Add per-route details to status, move socket to /srv/mc-proxy/

mcproxyctl status now shows individual routes per listener with
hostname, backend, mode, and re-encrypt indicator. Proto, gRPC
server, client library, and CLI all updated.

Default gRPC socket path moved from /var/run/mc-proxy.sock to
/srv/mc-proxy/mc-proxy.sock to match the service data directory
convention.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

proto/mc_proxy/v1/admin.proto

@@ -144,6 +144,7 @@ message ListenerStatus {
   int64 active_connections = 3;
   bool proxy_protocol = 4;
   int64 max_connections = 5;
+  repeated Route routes = 6;
 }
 
 message GetStatusRequest {}