feat(pkg/util): 补齐版本比较、网络与格式化通用助手

下游 OpenFlare 的边缘守护进程与发布流程需要这些与业务无关的纯函数，
按上游/下游归属规约回流到平台层，避免下游在上游目录里长期携带本地文件：

- version / version_compare：CompareVersions、ParseVersionInfo（版本区间比较）
- network：GetIP、IsPrivateIPv4
- format / value / string / slice：Bytes2Size、Seconds2Time、Interface2String、
  TrimStringFields、UniqueAndCleanStringSlice 与 IdentifiableTimeRecord

验证：go build 通过；go test ./... exit 0（48 包 ok）；
check_cordis_architecture.sh 0 violations；golangci-lint 0 issues；gofmt 干净。

backend/pkg/util/network_test.go

@@ -0,0 +1,36 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package util
+
+import (
+	"testing"
+)
+
+func TestIsPrivateIPv4(t *testing.T) {
+	tests := []struct {
+		ip       string
+		expected bool
+	}{
+		{"127.0.0.1", false}, // Loopback is not in RFC 1918 private range
+		{"10.0.0.1", true},
+		{"172.16.0.1", true},
+		{"192.168.1.1", true},
+		{"8.8.8.8", false},
+		{"invalid-ip", false},
+	}
+
+	for _, tt := range tests {
+		result := isPrivateIPv4(tt.ip)
+		if result != tt.expected {
+			t.Errorf("isPrivateIPv4(%q) = %v, expected %v", tt.ip, result, tt.expected)
+		}
+	}
+}
+
+func TestGetIP(t *testing.T) {
+	ip := GetIP()
+	// GetIP should return empty if no private IPv4 address is configured, or a valid IP.
+	// We just ensure it doesn't panic.
+	t.Logf("GetIP returned: %q", ip)
+}