feat: track WebSocket subscriptions in metrics

Add metrics tracking for WebSocket (NIP-01) subscriptions in addition
to existing gRPC subscription tracking.

Changes:
- Add Count() method to subscription.Manager
- Add MetricsRecorder interface to WebSocket handler
- Update subscription metrics when REQ/CLOSE messages processed
- Wire up metrics to WebSocket handler in main.go

Before: Only gRPC stream subscriptions were counted
After: Both gRPC and WebSocket subscriptions tracked accurately

This fixes the dashboard showing 0 subscriptions when clients connect
via WebSocket (e.g., nak req --stream).

1 files changed, 3 insertions, 0 deletions

diff --git a/cmd/relay/main.go b/cmd/relay/main.go
index 457a719..e4fe9bc 100644
--- a/cmd/relay/main.go
+++ b/cmd/relay/main.go
@@ -93,6 +93,9 @@ func main() {
         }
 
         wsHandler := wshandler.NewHandler(store, subManager)
+        if m != nil {
+                wsHandler.SetMetrics(m)
+        }
 
         var grpcDisplay, httpDisplay, wsDisplay string
         if cfg.Server.PublicURL != "" {