fix: 接线 Prometheus 指标到连接与投递事件

internal/app/message/app.go

@@ -7,6 +7,7 @@ import (
 	"git.asio.asia/nixevol/NixMsg/internal/app/port"
 	"git.asio.asia/nixevol/NixMsg/internal/auth"
 	"git.asio.asia/nixevol/NixMsg/internal/config"
+	"git.asio.asia/nixevol/NixMsg/internal/metrics"
 	"git.asio.asia/nixevol/NixMsg/internal/protocol"
 	"git.asio.asia/nixevol/NixMsg/internal/store"
 )
@@ -86,6 +87,7 @@ type App struct {
 
 	down  port.Downlink
 	conns ConnRegistry
+	met   *metrics.Registry
 
 	mu            sync.Mutex
 	largeSem      chan struct{}
@@ -117,6 +119,11 @@ func WithConnRegistry(c ConnRegistry) Option {
 	return func(a *App) { a.conns = c }
 }
 
+// WithMetrics 注入 Prometheus 注册表（投递耗时直方图）。
+func WithMetrics(m *metrics.Registry) Option {
+	return func(a *App) { a.met = m }
+}
+
 // New 创建消息服务实现。
 func New(db *store.DB, lim Limits, hash auth.HashPool, opts ...Option) *App {
 	if lim.RequestBurst <= 0 {