feat(nginx): Phase 1 - add /metrics/circuit-breaker proxy route

nginx/nginx.conf

@@ -86,6 +86,13 @@ location /admin/ {            proxy_pass http://router_api;            proxy_htt
             proxy_set_header Host $host;
         }
 
+        # Circuit Breaker metrics (Phase 1)
+        location /metrics/circuit-breaker {
+            proxy_pass http://router_api/metrics/circuit-breaker;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+        }
+
         location /health {
             proxy_pass http://router_api/health;
             proxy_http_version 1.1;