feat: add bounded process metrics and private monitoring endpoint

internal/transport/httpserver/server.go

@@ -4,9 +4,11 @@ package httpserver
 import (
 	"context"
 	"encoding/json"
-	"git.yuntuo.hk/k2safe/orbit/pulse/service"
 	"net/http"
 	"time"
+
+	"git.yuntuo.hk/k2safe/orbit/internal/observability"
+	"git.yuntuo.hk/k2safe/orbit/pulse/service"
 )
 
 type Checker func(context.Context) error
@@ -36,3 +38,23 @@ func New(addr string, ready Checker, tasks ...*service.Service) *http.Server {
 	}
 	return &http.Server{Addr: addr, Handler: mux, ReadHeaderTimeout: 5 * time.Second, ReadTimeout: 10 * time.Second, WriteTimeout: 15 * time.Second, IdleTimeout: 60 * time.Second, MaxHeaderBytes: 16 << 10}
 }
+
+// WrapMetrics must run after all Register* functions because those functions
+// intentionally register routes on the underlying ServeMux.
+func WrapMetrics(server *http.Server, metrics *observability.Registry) {
+	if server == nil || metrics == nil {
+		return
+	}
+	server.Handler = metrics.Middleware(server.Handler)
+}
+
+// NewMetricsServer uses a distinct listener so public API routing cannot expose
+// operational aggregates. It does not provide business or database endpoints.
+func NewMetricsServer(addr string, metrics *observability.Registry) *http.Server {
+	mux := http.NewServeMux()
+	if metrics != nil {
+		mux.Handle("GET /metrics", metrics)
+	}
+	return &http.Server{Addr: addr, Handler: mux, ReadHeaderTimeout: 2 * time.Second,
+		ReadTimeout: 3 * time.Second, WriteTimeout: 5 * time.Second, IdleTimeout: 15 * time.Second, MaxHeaderBytes: 8 << 10}
+}