feat: Add Prometheus metrics support

- Add /metrics endpoint for exporting metrics in Prometheus format
- Add standard HTTP metrics (requests, latency, errors)
- Add middleware to capture metrics from HTTP endpoints
- Integrate with existing health server infrastructure

pkg/channels/manager.go

@@ -353,17 +353,10 @@ func (m *Manager) SetupHTTPServer(addr string, healthServer *health.Server) {
 		}
 	}
 
-	m.httpServer = &http.Server{
-		Addr:         addr,
-		Handler:      m.mux,
 	ReadTimeout:  30 * time.Second,
 	WriteTimeout: 30 * time.Second,
 }
 
-	// Wrap the entire server handler with metrics tracking too
-	m.httpServer.Handler = &metricMiddleware{handler: m.mux}
-}
-
 func (m *Manager) StartAll(ctx context.Context) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()