refactor(backend): extract to pkg/cap

pkg/trace/propagator.go

@@ -0,0 +1,15 @@
+// Copyright 2025 linux.do
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package trace 提供 OpenTelemetry 链路追踪封装工具
+package trace
+
+import "go.opentelemetry.io/otel/propagation"
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}