feat(infra): add OTel auto-instrumentations across all services

NestJS 6 services use getNodeAutoInstrumentations().

Python 2 services use FastAPIInstrumentor. Go 2 services use otelgin.

services/push-gateway/main.go

@@ -11,12 +11,18 @@ import (
 
 	"github.com/edu-cloud/push-gateway/internal/config"
 	"github.com/edu-cloud/push-gateway/internal/hub"
+	"github.com/edu-cloud/push-gateway/internal/observability"
 	"github.com/edu-cloud/push-gateway/internal/ws"
 	"github.com/gin-gonic/gin"
+	"go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
 )
 
 func main() {
 	cfg := config.Load()
+	// 初始化 OpenTelemetry tracer（endpoint 为空时自动跳过）
+	tracerShutdown := observability.InitTracer("push-gateway", cfg.OTLPEndpoint)
+	defer tracerShutdown()
+
 	gin.SetMode(gin.ReleaseMode)
 
 	h := hub.NewHub()
@@ -24,6 +30,8 @@ func main() {
 
 	r := gin.New()
 	r.Use(gin.Recovery())
+	// OpenTelemetry 自动埋点（HTTP 请求/响应 span）
+	r.Use(otelgin.Middleware("push-gateway"))
 
 	r.GET("/healthz", func(c *gin.Context) {
 		c.JSON(200, gin.H{"status": "ok", "service": "push-gateway"})