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>

ARCHITECTURE.md

@@ -487,7 +487,7 @@ addr = ":8443"
 # gRPC admin API. Optional -- omit or leave addr empty to disable.
 # Listens on a Unix socket; access controlled via filesystem permissions.
 [grpc]
-addr = "/var/run/mc-proxy.sock"
+addr = "/srv/mc-proxy/mc-proxy.sock"
 
 # Firewall. Global blocklist, evaluated before routing. Default allow.
 [firewall]