fix(observability): 治理SSE慢请求虚报、客户端取消日志污染、退款重试刷屏与会话计数慢查询

backend/internal/modules/chat/handler_error.go

@@ -1,6 +1,7 @@
 package chat
 
 import (
+	"context"
 	"errors"
 	"net/http"
 
@@ -10,6 +11,9 @@ import (
 )
 
 func writeChatError(c *gin.Context, err error) {
+	if errors.Is(err, context.Canceled) || errors.Is(c.Request.Context().Err(), context.Canceled) {
+		return
+	}
 	response.RecordError(c, err)
 	switch {
 	case errors.Is(err, ErrDependencyUnavailable):