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/format.go

@@ -0,0 +1,70 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+// Package util provides shared formatting and string helper functions.
+package util
+
+import (
+	"fmt"
+	"strconv"
+)
+
+const (
+	secondsPerYear   = 31104000 // 360 days
+	secondsPerMonth  = 2592000  // 30 days
+	secondsPerDay    = 86400
+	secondsPerHour   = 3600
+	secondsPerMinute = 60
+)
+
+const (
+	sizeKB = 1024
+	sizeMB = sizeKB * 1024
+	sizeGB = sizeMB * 1024
+)
+
+// Bytes2Size converts a byte count to a human-readable string with unit (B, KB, MB, GB).
+func Bytes2Size(num int64) string {
+	var numStr string
+	unit := "B"
+	switch {
+	case num/int64(sizeGB) >= 1:
+		numStr = fmt.Sprintf("%.2f", float64(num)/float64(sizeGB))
+		unit = "GB"
+	case num/int64(sizeMB) >= 1:
+		numStr = strconv.Itoa(int(float64(num) / float64(sizeMB)))
+		unit = "MB"
+	case num/int64(sizeKB) >= 1:
+		numStr = strconv.Itoa(int(float64(num) / float64(sizeKB)))
+		unit = "KB"
+	default:
+		numStr = strconv.FormatInt(num, 10)
+	}
+	return numStr + " " + unit
+}
+
+// Seconds2Time converts a number of seconds to a human-readable Chinese duration string.
+func Seconds2Time(num int) (time string) {
+	if num/secondsPerYear > 0 {
+		time += strconv.Itoa(num/secondsPerYear) + " 年 "
+		num %= secondsPerYear
+	}
+	if num/secondsPerMonth > 0 {
+		time += strconv.Itoa(num/secondsPerMonth) + " 个月 "
+		num %= secondsPerMonth
+	}
+	if num/secondsPerDay > 0 {
+		time += strconv.Itoa(num/secondsPerDay) + " 天 "
+		num %= secondsPerDay
+	}
+	if num/secondsPerHour > 0 {
+		time += strconv.Itoa(num/secondsPerHour) + " 小时 "
+		num %= secondsPerHour
+	}
+	if num/secondsPerMinute > 0 {
+		time += strconv.Itoa(num/secondsPerMinute) + " 分钟 "
+		num %= secondsPerMinute
+	}
+	time += strconv.Itoa(num) + " 秒"
+	return
+}